diff mbox series

[RFC,v2] Add a post for the new TCG cache modelling plugin

Message ID 20210617121707.764126-1-ma.mandourr@gmail.com
State New
Headers show
Series [RFC,v2] Add a post for the new TCG cache modelling plugin | expand

Commit Message

Mahmoud Mandour June 17, 2021, 12:17 p.m. UTC
This post introduces the new TCG plugin `cache` that's used for cache
modelling. This plugin is a part of my GSoC 2021 participation.

Signed-off-by: Mahmoud Mandour <ma.mandourr@gmail.com>
---

v1 -> v2:
    Elaborated some more in the introduction and broken up some
    sentences.

    Changed the example of blocked matrix multiplication to a simpler
    solution that requires less explanation since matrix multiplication
    itself is out of the scope of the post.

    Added the code for the `mm` function but did not directly give away
    the cache-problematic portion and preferred to "investigate" the
    problem since it's the job of the plugin to help knowing where the
    problem is.

    Added an epilogue in which I summarize the work and the patches
    posted until now. 

 .../2021-06-17-tcg-cache-modelling-plugin.md  | 266 ++++++++++++++++++
 screenshots/2021-06-17-cache-structure.png    | Bin 0 -> 19675 bytes
 2 files changed, 266 insertions(+)
 create mode 100644 _posts/2021-06-17-tcg-cache-modelling-plugin.md
 create mode 100644 screenshots/2021-06-17-cache-structure.png

GIT binary patch
literal 19675
zcmeHv2T)Vpw=YdV4NU|hEfj%Ik*4$(6ciBwMUYNJM0!U$1S|wailU$*f=H3B(mN6n
z1*I27T0jg%AoKtsdHV#v|JD2Mo4NPRn>Vj~GYrEV&e><}b$0eyzp`@soS`nu9^O4P
zG&C%Fr*({JXz1x_XlNOj8Nm_1%BeRrG(t3bI>$`{ZRhIt_L`ZNts}Wi{@P~KJKDxq
zoLn36kt1w(mi<_rPV>R@qwn;y?_M~>qOf>0?%D~dT7rx50Ug^D=XF$WSNNs>1;dz`
zFn8D1`^(ct3K=&(qdaQEKW7S*_Wi7~KIlqWTUUC2K;Tk1{@L;|ylsQR`XpZbCL41E
z&2K+iQoG%Z+Y0W<|8@-eza3nQ^Uo6vc3*<ObjICN{Nv0^a4oj~%6VE7`-svUVUMH9
zMibf5pR{Ngz|Ro|S(y3M@x63HG;~3njj{;=VeA6XZ5|lXV6~>jv_Q(}gkEt(da`%H
zMF#IjU)|SLaeGQsMD<~`v~b4f=qY!RO>T~DWCo$l3+Yi$-+3#VEW=@=t)mX(*U=#b
z(BGcY5aB(e<H^y*b9+i$WH2uJ;=Zo++fJ-5w9rk3&dJch8D~sAuYed5kdZR%UDhI-
zqo4V<LvB0yFTdZG(dkWzww1_0ah&JmNCo4nTWjguh<>TYQKzFL!QMsIS$Xl}_$68n
z1Mv){Cro$nx2Je?R$N6?Bch4Ql$hv?_;_ZH>(s;tax}`0o!l1=O}!D*$Sk7zEIQ8J
zfBlfiX5~hE<3*j)jEw~&k&K?(Q(huZdev#H2S}b21jlx2^eIKkmfUA_hZ$vyqsu{O
zMOWl<4O)@%?U;_ACWpp+B4h2&qcDl2iHbaIvRe+^vG+C&3bz0v-d{>~JEN1#*~Rf0
z{q@Dh`RCfVoftU`+y(box+;b`rcZWEL{A+O3C?-An3IBGTD!5cQnU=1!E@Jpeove^
zLd$`f!0si&5mwljoi-{k=17(i&nRZ^dh=tQ-cVFTkdfF<gJfJOx%!z^r}R#=;mFv)
zP0Ogrm}n<K4tJXahne?7Pg^UU9VC0t+dVl@=F`PrX>fd&$N-PXNXL(fLt}t+UuKjG
zenKbIY^>-9&)tn2Z45_O*5?~^4M#|B%dZ;a8Oq4cUHt)jzTo?G{M0zY$~Uqm7UU7S
z0_r!R5ozf9L?Z0cEmu#Jg1=XV2nHgXyEzus=;GxmPuP*8ln{~4v&$12FH%sO+Xl;O
zG;SRY((h(fDNj1T{6KNKc*4g}oa4y}0dC=*W0oSD4jKdzeRdjJcA7|T5P0X_otymn
zeeMD{=3*I`$wFO7)cb>ff%EA9XU|iI5zy^|2<k1tU3Y#WpKvf^wJvb}h<wr~Fuk*s
zcAj?c(?;<Ww|(L9yjZQze6-Uye*1j)#)Flx*~fq2_k$5yLJ@W}v44lU6Q+U~$XWI+
z-N8Si2Ipz~bKd_+c@bI`G_UcOGI)ISmZ8ezgIJNUxv~MLchMXxO?zd|72DQ1HQn4T
zf2lFz)3FnQ*Tg%|BabD2OqA&P>X>GbC~lC!X{h|X{bfSPE@r>p4m4>3G5yrH{W%XR
z^j`Tl4>evj|04pvpX9hc>=C}Mr5>p(7<6-O$k%Al4kIw$T)01mTPnjdY}RU}U2UPW
zHfZ^5y-*U^u!S5=?}&M>=*9~guxS#<PPI^4&FW9+@_RFE6EMikt@)bxddl`f&unpn
zVTyaX#i7^Z=|Y_cBI7nU23?D@EK06+)hyKO^H_V)Mn$$?8Xwh{0D&)*bZD;3d7@M5
z*XtI#ux!Y)*eI444dm70m0Y8+yp>808s<Pw<+U&NSlh`q6#32I>K!i0>*T2y@!1EC
zUA+W9mw1=wGCbNb`(lA@-II3p<+D$YIkJY47F+x}k2BrM-x#h5V2kaL*!S({n>J~A
z?{S?$pEjx7fQ6A#ziH!{(FWw=_u-`=%J#bRfK31krN7K|fH1JVxhgtxP9T)<b_OoY
zKzoR`Bm9Sbd#YOU+He3$_2(;W6PM}GfrN{6{(=nZTaOpugyF&-BV^d{X6<UfRgZ6n
z22a0xsFsi;ooD@qcxv!WF0Ki-VA`%aTkr~r>v$w*Kh<yLDK?@m=<`9?uETry+CUeY
zj7N8`ee*=jM+l%vi?iJmYW5@sdQU=H;P~ya<tRQ6W}c%;qyp=z`y(L>bp$j?AVQ6P
zx|#v2rP?olZN_A?uQ;5mXrF?DLf0)G+tb<@Ru&X%$XuD3^7+k`Y3%`PUzX3$G*Yq+
zQn=;SW!(ZDBPe0tKipgC)|V-48_P^I%y@f)3B$>QVE^k$gd?&dZnaaJty%V*-{Kfr
zl<wr}F~rn#PFl8S=mg&ih`uX3#beK=P=Z3_Lil<OuB%*MrtU$K3`$V?^3tx>7Qv9a
z()Gk~uj7d_7ngRW9KXSMD`#KeLQ}{?mIW9gs@`+79yfhUG+zDweC0%(EQ}zSUDuIl
zq<Py;$QyGBewz6yUnr4)vlAM-U2Rq2ft#ur^4U8azBRYfNY8c?x$HOeLYHlmfMuJ0
z7BcVb3nyX`WUXXtA3frI=M94COPR1~eR-GOmp3hN=dOv3eeD1*|G|?R-)&5g4U6yj
z>^S`<VwLu>RTCq$<{5}H$OXCZwUV?h^43CwM})@2-D6Ji8f(n);>(ycr^?NleCHpZ
z9t*J2llC*PaglI)A8ALycHfYTiVRhy#cGXP68a>_#$%2K4I7_5yDPmXoJhn)zm3V{
z3mwli22Nrn+OO~08{LpTSbeN9Q6=rsULI-d9GsP}uE4eZ^RR<O&Z%tpJ}AT?5aRrB
zN9`i++T($s@UwIX_Lp?D;h$oaHb^&ENvDr`k~c&|*9jMlG`QyX5HJYg%^|#|ZinWU
z8wN|mh9#YlMH3B=x1|}WFX{xZbm?M8kt?0rxbu$Wv39LZ>9?{8&w`Z4-#D~I8!?1?
zczkoOV2P(61`CSsWY38Gi5MQ4?9_mf$3*l-Dm|HyLQ+?T@hiW|Eb#hLz3<i9v8c#u
zf5T@%AuGoykFYol!cb{6)He_b17V6pnxVoJ)c356Qnp8NO=3t^zmXuk`-3yO@w>~E
zU<9>zMA*uCLfL1<Zv|V6oG|)nwOv@P6F&w}XpJz!TPEB|J~BbZfKWq6I%Y{~<0Qd`
z=W7-WJHTf;@Hl2J$0*Iv%;uVD;HmhSzD=x*<&w;v#Tbo%;cI4rZqY_VNj!Hrv!k^8
z5+VYS6+-XS=oQ?uVa99ojw4!&`U#<3Od!O4wBeKl)aImtI<lyCG<@q;%VP>2O~!<S
zO%l^`y?oF`vU)l@#cBDoQcjPdS}b{PlpI@ByVRQQyzLw&5kU#ZA}g9f)SDh4kqIiO
zW;}j#qhGE;$G?%5snaujImN53aB|@0#X?Ii!=vGEqlyX3R;wia6QOEFlZsaQA3Phj
z{ox0R+yV_ZKQ-8P`J_nMSt^?t><(N%wmwhVSa$yWM4>lJKiMmeaPAZGV>BD{euKu6
zv<(efvT3DM`IpOeuQrBd$z9CU-6iz+eRTSjkN3sw1b&1uB3nPDNfuR#49$&S+l)bx
zE`Py>;`XALwdp9tk4E83i3HzjskBFS5u^9MAHRvdbZdJ#{q4eE1etxf3rA>S^vz4R
z0{*T=s1?bFBv4wo>ECGFso{V9PB#ao&z;G=3xAXm2~uE$uStxNk-ya@5n8W7-M_z$
zXXH2)1^gO8$O??`Mv8@w{$I5Z_#^T%fFFM)$<+Q?$drQ-u2}IhF#b_|HScSbJ$D2Z
z$n?huZeWBD<?_rhY7zSPE$={ek9j?T^^Xz0f)Ntjo!Q}kfSvvN0FJy4#R>c|!W%Gx
z(6??O*+0_rSCSSEOM{>R8)l-`g$oxRV_IGx2Xiw|E0HpAr^9Yqrx=TN-Q9ig0HfC%
z$01r4L0+XwM~dBY?-<L4$d%fyuRW+;1mSmgnFEVEMsn@y*2VXrUo#jNf{oy^B>mPI
z4g&ej;+ol^N6h7ZbR*mNxne&p=5%8QpM{2@iF}jS9B%TF54JIOLe=W*CbuKjKYpJp
zK68Y_b%UXHtK%DL<0kv@hs@tc&{ZvFS(c*xfpmwq*sxlmVd*c~X%`YdenZ_lC(;XJ
z4qQ*GXn?T`-`vCTp^oAcUwk6#)XP28lOr;;5=<~VBdZ?daAw^Zne{Ha_O)Llr=Aft
zW}$|mbwSwauy*6tm8CVa0}0IXd#N$Y>^;q#ar9TrXP<Mtyrb1h#>%E2=Fl+}9t%4f
zw3WX{_uXSA+6D6RS~8QE&Ur4ns&&--qG?up^aWiZ2Z|lMvyVCN4m&~faqYG#gJ{#I
zn-Kw&psh9r&Zd{lkwaTD>%_yxS8wJXOn5_)h5Z%7V4=Vqn09uAoOhh#{ErijHI&-z
z$)?@jCO5R^x06Fc`(7T+=-qevEBY&pp8xc)W)kHQL*U2iW+-xrHoA*Kgxw&T#7%54
z=Ro9`*o4>|^05*+e`sR411{(*0`BsLm+?r-#M3>0-EOwLl5e}u-cWHcw5)o~CwUWl
zRj4SWQUAUEAo{5160T{hvYXiYrsRifU-H9>wMuZBs{7N|s?MS24dWlKC*MsjrCb?N
zEpL(?JANLAg+}A>$=&B(Z<*R68-cqxa&+X{eMA+%J~$$<sZ!K_vHfD0b?Ky)>vG?W
zvBQyABbVgE^BM8>p9k_}RFR$(=mrKPIHP<ozkI)l)hg?ugV&yaHp|EUI8;>o`^B9d
z-U<~y<uel*QlpkB#TSzg+dGFE*O++ogz>x9UkvNo2-+I>k>BS$-Xfd+{73q0?yq?P
zr-gI(LXjvMc~6%8b}=SAF2Cwwi7A4|eWM>rg~<W^iNwLIJ2g`i=F4R>G3_1S8Wd55
zhMdSKS{4PS*s>27>$Lai**Jk|yb8J_S^V3@sw=+Mp9`NBZdN+ARrG@pvRch~(|V;%
zhfX3|o)nv+{K7}bWg9Nno)G0=PA^rQ3Qm^K2pFH9IRU1D`Fz1T==Y1Cr%kwcOuF^8
zoV2Ph10hJ8zV9Yx`sa>IZz}hP7H(!NFRvAY1oga&x6{)8eB55@jp;(d31c28lWxz(
zTU~#<n01@q%vaJeUsHN;sSpYw_h{04i86hzfUcI;;2HCzrd6P!hbJBmqvv&D<#oMR
z7>wC}zq%7l!)|%MneFcvPvI+{SgBa8dUqvx7J?A;AHJ5?%(cm@jM0o!K;_p@k!rW0
z=PbWy5AQtZ+i4!-)~A-4(0dC^gEb|ma>??yi?xw0eM7BZ^WtO5LtQ}#HhFim7WL+g
zn{8IS3pOlQPvY@&D3G9>+X!q#)RP<U!CD&;zLhCm3a0Tzz4_t5Zx=&L?Z@w{<)5YY
z|I1P{^MOB73y@CrYTCVmM^b`bJZ*{P(_Q}Y`NeKdah>I<51y`$#dT}Ev2eNTwt=`^
zGky7H%KZ_v^ciuEQa*R<-E3i3m%e}WTl?zRlc|?@V(v0hZlipykh=VZe_#HGwyJ)v
zGR`hb^d*I-DRgiC47;k|p_H2%5bCh;$A)R}6wYXQK2iD^YNOR`Dq1uy9YH2w{6@pp
zyVe^hVZqz01I{I%6*&hQEx*IVzM|R(Y(u0#B^5Igwr*2Bc73lb%&k+*VSp(mXVc?Z
z=4^CtQHg=mofrl4w295Cd;N}!Jg+*>4Xzv4@VB!Stb5~iZK5VyS?M7#Y9FT(HD5g|
zJ$N}rY6@VU3;<=$&&s4EqrxAztKj)9OPx5b&GyH>zk5I%0tKmF>%##(V#(GgB+ZIo
zs`b?km)>5#7Qo+MV4;l>@P~)ZxuRa|m8ta_?p_3Fqo=55{)~RIbXJi~O;p3eKrv$R
zdN8Pl_a?(L9yPy^%8?5maZ75>cUb%uFd9a0RKzq7D?oL<!O()Osh*$LdHJA?Zl=E!
zKEz^{r5|6pP;$yDtr^vLLfd&%f6fQa_-bSzpl;#ioTM6z->Z?<jz)QVrDys_iYF`I
zwwY~^!?0{4r9a0AQ4Ij{6odjdmhnB2OoFG?xd7GhWOHp!-w3%aKL=2n-;j4p*KsBR
z9l#lUueQ4c&||6poaN?fF}hB$;cJN_C*>PJfu-{cUnyg6Z%h}IwC|Iao5n=G2`ppu
znR<@740n2=-OAtpDkyLLhhFvVdxK?e{;igtuQXf2(i8?akC5rOdCzRwx?t=!I0>dW
z(;U01H`vC;NP6durAbg1^K1g-|1xBK{vBV+H;)>r+GDc8D^ss<ly9SCZr*q#$(nMK
z$3~|uN$Q1jPj=VJbPsm4*s|;}(YflF7kLBU)0=x?`YjW}I$*WIVGhEK?DKySgu0e+
zk>B-EoBLvU70y(?dzT7xSBcel+&bRpgi<t~H&%0d=7(Z+a98Z=NR{zcA4)14xfB++
zrRiE4K3}UgaU^rLvX^yMqkroW>)q*mc*ES>p`e_h-rn9Tt9{wFPww^>O<qw2B*t`M
z#fW9VCnNM`5AIejATVy)jeR=Sk%_}%iXE3h8dIZK1$YG)?fB|nbZ+)6iM_u;i@feP
zTUg=opy#QI@6_F6?diAn@)T`VOvEFf#i`D`ELea&XwL7dcgqYrT;@9M==Mwzck*;8
z<HM@2I>-Q9ks>4Nx<L2oE`{|wZ4U(nytg<#;GHYbA2KX^u7BM=wLQLd<iHqyd1DV!
zqA`A(phgRUKr4?bhdMR-(Dh3_21+anbATza37*bc0m<upaOlDmSh{TJ4lHeh+N&!c
z_l@gXJVTQ=2o1>XX(KG5a}(S0B?zC2eNFUWKm&HEgV0W^RItKX5?HF#-0b!Y%B)0U
zsfV!|tfE>5^F}dc3g2#~JaY3tky*(g#|YHmWHM$Wj|8X(wd$o-Ni2Kk5}h1!wgYer
zq8buup+1$aULS-pH`7EXTdoJM&l`ktIYWRxfc*<<Hh_`%^+I^p!%-IEPe){ppjtRb
z5~>NOdrz5B^L>7CeRY@UNdc}Fu$O4yZN-bZSpyx@=i(ZF9GZV!bu>s}5G>ue({q-J
zY7Rw8U<ax1;B^iw_lQ>P)dx#=z$g5Yd0Y*rHFxnTs|B@hi5ETKf%8@PrUlY+N63;<
z$kJ_P@9}qpeO^`#;=Mjx=$~I+<9OVOzWCIDs2T>ziv`R9w2CAJ;qr~QY~flEU<^d3
zuVN_kR->ET8e2b0aLKob70VlKGCy|msRx$8=a{dAy+fqE1|(+g(OjJFD<Y3>CPGT4
zu&Aywlbq@QMSZ$xKUfoPnV%C&jk5edWkWl!@6fu1Xkkb90%vY&=|Yyj`NHcF{gC*%
z%bSPadxnIxwzAOoXZm(pfwBYNC?w7ZRTZsvG@$Z0S?p#TTN-r#8N#^ck*}(w6;v^{
zyA|-{SkC(54}z)`W2X`hZw!_RNp7#c>cwUce`RbkWzWsl(QL-y!o3fKCOs*eu<MdN
zJ18^i<VfFrpt=&29q;}rJN~I~|EX|)!$bdoDRMy+tpS~Bzr2D%E*9U^H}?WJ8Fo}}
zTW^jxD+&T}dEUJMU<JYGP3_%c%}Pc}`8j7x?$!q&+u{ya+y@9P5uxI#4{cH-eu{C1
z5Dda4ewIz&Ey&A0br%pE2UjtlwHzN>P)6VW!tOdF<jj^^0?e|2VKCxF^cPo#Gs+y0
zai)B%z2<hyuJMLQ=oNh`+mS4#%#b9uLtu!>Gdz^q;UwO$dP%?f+Y2Cdgw9u(%1=~2
zfEoITQJIgnhkWC$i92LQB5y|P!ySI2s-MeygB|b_aK=y<Mw!R^sLY4M9Tq!>GgLBT
z=TD(^a+^l|*|s~co-$|tY;cRBRoCVo&;W!5$W72zq64iYI}xHv^tSElZqI5F?l0b7
zOZ$}4U^>6J;RuUY;Q+U=V4+V!d49-^xNi=jXfe4TS6%=l>M9eEi*#cguV$*fQk%Ig
zu`G^|u8o(BEk2?KCD9_tH9jB0%<m86C%(t5O2!=t{1~XWW%Q%aUJ^zxxSvZC8jVXh
z`Eb|HbAfwIN=?{EY}{*m4LvCU%4ghu!`1(Q@&+6x5{OUTP;vF(g5mA)V;)1wPn0|b
z4Iarp*B<snZ&|6%mG)$Wmb?bsNmvN260eM>p)uOHX6pS%lS_d9>DaGdW9JO$0v`cJ
zUiUg@+)tYv?uOX+`F|PO&PD=aA=S*<VGCj@l2g$?7a{iI^<vpiJtg6c><nA~2jZe-
zF$POOJ4)|*q1$tVO%pEm5Jvy$=W-fFy>5LZ<b1uaAR}*VasUeY;9cg+=~AQzyur1I
zode@<gk4Hkv!}v6<ZVx`nz|t_o5zV>Ele?uk9q99df(hJ%yF!l2bIYodaCohuE0s)
zA;<tscehOV;@)b2u%`OVP+7&{tND;J6Q%C>=@EzGcD`A0wvGSSTjGXKPlJ+FY;}HE
zZEACU!6;sRiFp`EdGc33!7WR!vVhbWLWOd7oZ9?pL^x46)%*Pc`H;1r1pM~ew|Iz<
zpNFY0e>x`b^ZmnE4v>^qz`UL^vheBvr7UZ@C#MI<Y6fiT1TFZU!8fk??EQ()r8ENF
z&knW*X~%;+t9{fP9L)ZG&USUL2X@c;F3$Q|KUA$Ke~L&ASs0?54a48%-Pk%mi1vOk
zSl%8CA8YXgD2k6UlAcXH!BBJKN-z+Hus@y_w|dshm9Ml)7T?tMSQ~Ve2_C;K@zN+w
z)9<swz)gegQs*A0nciGG?T!FOAi2^H0`<$8Oxm!!qztOS8*9l8BnS9WaieEvk2$ty
zHURY%5{13a_OHzj#J6j#TdS`2UYG`wVh&<^O1IPtcfztZP;TxOmenp{%qYY^H;R^U
znA~<M*yr-{{tETTUtHw(c**i>)&)v)7Z_zMn1a_!e!ldPgy_oeXTR?IwHx%mHeJKg
zpdwMFPUk<217-Dvn0`_xad85h22g51^>Vu!Hli`buU@qy?V+TZalD{LllV4J>MVc|
z)KF;t8q!+wFSR_;OBCOceKBlo0c@vYdAZ233r7jwL2zOVl6*YHvtH%eboVU?#}7h)
zLLiz26S?-&n3aC4Ow)ZKQE!GVC9-mI_pi9FA^_ekHK?u&XDq%v;0QtBOgvw|%%Lu$
zpMP_*TnNTE%}u9ZAo6H)0~8<hWeOFx+K1~1nXi%<_W$O-^2I*>7JBw;3BKAbSq5de
zm-|RM1Sy7P2_0ziu`e1xP<tDP*uv@FA}&4$qP6-^kW<isKv2l9<RG^XIV}LJOi<p3
zw0zg$){&~FL|TZ#YK8b8!hn3QQS*I_{onHa6HC*dQfWt1d&ed%D@>*=@tLQ2L#B?J
zAfxP&<bd!iXh*F#flH!lB;`)<DXclKTONKkdV#^(yO|5;odFP~Dr_IgRZAWA6bQw*
zu5^%l8Q@4FEjxdG<AA%D4yF`K1!sSCt1Z-O*9ET*I>CuROz$qT@xW@O2I}$nP8*A_
z4vZw<$V`(P3O8m6hwZApv+Z-btK*ubr)8dl3T5^k;Iq3|zkW01P0JdAa6-jEMK^hQ
zYAXuPNW3)~w)Rz`7Qjc=MYUa|%Y@Yd6vCEJH<Op|)c#ZjH={YqMciIMBj)$O_!N%}
zIS0<<=0u}4qDSQdfkt_I;V|Kn7a%<_xQHB6LAq-HIbK1;xEd$PmKJ%q6bOb4TS_B=
zFKlY&hig1dBwg=G#TcaqTBvxME9WBh!)8hk0C47UAbBmVH@`P6D{Z!PByhzS%xueO
zuw%r(n|K7z)W20}mu?8&W%#aj7CG3@1`2sL+#niF8$G(a5*NkiG}ai2;|V9)M8qS>
z%A~u)3BuY<G4Dv@3lGg~^;!f1tchIDV`S=;YlS{((<4>o0|{e<aGFt-F_e5T@Ec4Y
zOWQaLXCR&zU2DNIA#L9Uu*`#d$hws}<_w#>KYO=ZGWXgzwQ8}b=l?H<Y{5n^xckQp
zBoJttNy}m54>Cc!f07JF)t&KG(0#wf1~>4YUOl`DY8^qP0P1UcKD1WaW3pWjR4-eV
zal8JgUNV|65C<>v-B=7Fx@XUghYcCy_Og0_Hwn+pM-Oj995Z0M!+&S&{$aa8z4U}3
zufW;G#Te6ZEB~7=wr%Um{msNdg)=OLfMqwGcnRvFWjJHr`!Br3SL>Wr#QPl&ge`<8
z37C3_0bDGB^chKlO4izGH~v&e62VHO*lBU9%LBU%kmaa5TKnM=a>I?kH)P7L%elxe
zky<d?h446)@^=@(^OV^QJbn>>$VVKSZ+?}P-28NH_jk(5eZ1FOlXl9=uiV^`RXb&+
z^%+Kqs-3cOvX#YqQg25i(_=Y5d1j}qw4S|F84AiuB#d5D;YRY=-BdyCXmix7qhe#j
z=n?YHp9vw9NkLS$!%1^P2IDnE6m3q%TZ3l|wMOEe=pbWl6L6Dxq$j${N837RA5~qH
z>Bti~EVH97n)QuI=+lizBvv#Wc`p3Y4and?igbG`{OZVVs&1L=aGv7<A5~p!EOhgF
zAiASl#(iSHP`@KZ)_-TWh}%&Y+g@i!e~hQ9i(_U=fvpKt-BL#T3iBcR9Vyb@k6B8a
zuAgjG7p$<o)j&~8^=()28+6XO1#5{%7$r&=WrL0WD5*+{@6aCC(C&#wR)#@H?~{e4
zGx0sy(LtZ%L{$Q)<8^4*DZ4p=@wR{uB^R)gD=5k;%5OR=neifzjUR^%c&z|}bdZ2A
zcgs9ixTqITug2ae8zD#&Nw+&t=En$m&sl*YKHyjYYNo5!_tUvrJJKhYId5fq1T>S>
zNZ6h@_B*0fxF9L*8|a}!y>&6iW6_-PUlOdf!<Y)wj=0Opr3<^oLB$JPNy_|62dSuJ
zAffY~iQP_?BnxD{p6&uEHLJ0UKpj#2o}fMDo3_RO`Kd}G;8Kr=ZLMWZwk7ur2aFmx
zKJ`AuZIIx~ZaRU7AVphQd$gp{&fL!wy3EEXpghC+h?D(jzJAelV(k_ac?n9FixSMO
zV%Q&YCGjeI39%qFp8^XKr>(kWrI#I%Vr8q^nlH9=JKKdsT`2vn7w6hWpA=Wrg9AXh
zPAk(iwL%qa1kdKbm#HAPg~4AA22T!;UPPNtBrlO(4$EG07oW;MNd;eySr%n7XxI9Y
z&Ai2BXswN`MmD?`hZZI`s;@tPsJg<11TD?Tp=z$h%AG}DCBD~@#fZA-6+&qf(j|8g
zn{^DW<5vh30egZZl5XiBHSNovxaxV+b{-OGkC3*}&O-|7r>kEQr7n)|W@w%7r>WuK
zA04*ti=dvIe|&dBhUm`7{Q9(J2O!BA&Un;~=H_?Zos*LfsrN<hoUF}~@B*=OGU+g_
zk;-rSw1I)a%!9Z3QSJW=1nTv*WKR2c_mNbAJ8^K*=p6TRAT`=@J7`{{>b8&dC$Iz_
zGmc+q(W>PloKgL+!=aG&D0xEKGy`mJC9L%3KgS1mfvT(Zr=xYjy}sze+S!9hAC)BP
z7#3&#)7r0k6c94LOO5{n4gb+=|FH)Ao3G#>YrwyEp>+8FJ6*c={cpN7e(2t)lcPH`
z8Q{il75r0enR=p#JM<Fr|7ouJ<B`4Mn^Nu|?J(0Ixkta5rS~X!&c2w;g0$%XMf2a>
z6wCAYJgT}A(r{+hH`HH1G83QD+pbpshGYT!EN!h;A=Xr%hau$i5O4x&H)3<GqQPKv
zYh-;2I3u&|uu)wo%BI<7Z;oc!vsTORrw%X{)vZ}RQE=t11Ab}0x4U>Q!M)~NOy+C1
zR7{5)1a#Z<^RcqPd{ofkEr2RpRgtb~FU-PQy$D6vo6pxuD3&@suv3|}i%{wgHQffn
zaRzV%UiYY;7Uz|BVlS&dMp$Z-!ALGb7H*H>>Mr0jcKVPY{M;5`awQv|k7A`hldb6!
zYP$iVH4kX90}8p{7duSXK>eCRHKA$mK)yEs>QfTPjorh*!;G6}KrGj9&F>93sQAt8
zSnyaRlT({ig|$%$sA;^eZLRbe<v^-6`djd9;dB-L*$bP1;WC0<x=Ssb8D%#F?y4<N
z85bMuNMmL^QPgPq&`dvxwCgo6UT?-zi1CV?$sR`)_q$#@320lZ9TC{nJ1lOrwYgBg
zd--MFEKk&AC96v&H0QAhdRAt78qXr&sQ&S)3qASJte=IR<QcZP^1MyD=B}aY^uZ@c
zw5CAdSmX+DoOc0RLM|{FuYf3fAWjG%IDP?O3itbdPq&DV@l+hY9%<L&EQ%8Rf^`aL
z*Kl?sg{X{w79zbk_8Mr*U66vUHoCzIs+U@9JI)?G!8e*-F%lf3IPBNcgo!-7tO|$#
zIoK8A7ruIapv6B6TeGMpZ_Z+GG24oQr&Apzz?fG%;&uL&W?Mr?-W$!9)WTFNeau4n
zJnWLWN1CT7!KD<M+a&-!OG7t&X1cTXh5<a>TNe@#3@qu>z^}j8Yzlbp1r$l>t#6~z
zoVX5Pw3y0>k<M^vOX`9cB2ZZ27R&&>MJgRSK!yE)Gg=wD!B$jrXSDiS5IhioQ^@eX
z0;Kb(mT)3BFB%xpj|>9OuXFFq^K<@Ne4e!&jPc<2y+GmB`lf;Yk0uVbrW<eGCezRR
zl?6B^ba;mk#SYwFoM-{A*ty<Ltk%N;KCnnf9ZfCL)J8{IEX?~uU~S&uc#uNV#=TWp
zub;15qVi{?(x_VZ>-+!Gx?yH`t8by(v#6Zs+L$P-6*p|aeoM4@2kNpqoFIA{<kvMt
zpbc<Kle2yKJQ_eWe}|=~JVug~_l^pW>Bh$?k4F;%F#JBupg%&4M3Jdm*$4UMajfsV
zbP;pG4zHRmtgu?9LEeU@Dvt@15o$K~)ow`f?BU&L*E0P(YRj~V^37B$tA9mp>Oko}
z-{PnN;|HdH+#V#;$NydlPoI=~O5Wb;$x608g9s%Y|MGMcP1zPk3$hZ2BLV+)GZw$x
zfkcqk0SV*`7gQvjj-n0si{4(uj5?34!)(#p*HlRaES9|~UaV~Wp7c>;4K@|i?|t`C
zriS9q!@P6tEJc~`ZS)GUvgev1b#{xVVsKM4e{geXV@<QY>CK3}c^n^OUTgmOsL29M
zWcc>xEuexQ-ujPJaQ&to6}-`GYU36v{75un@iFL(n0wtKh-0POa@}rk{Q0#6yG0+G
zHC2+f{WCaK@&F^z<82h8-l{Qx)lhx$9jlqZv<T-hn8`h}KHx97=9;OdRC%8lEmp>g
z)#8FuImbrt9+qb69v1g)CcwkpVnOam3kyA%(rLVIIhKY(*AdMj+GMXxlGNm%dUu->
z+qYH@I2X__0a&6MGO10TR0UCmHrKf%FW#)7;Uhm`|3(^PLZ(-YhO5;gJ2zi|pk}6}
zYkuyV-&aZ=0t_hMa9D!$(Qdo+JGIJ6Bj*S)qog)N(iHb74yRi|oXqcsRByvp8yB-a
zDBQf7`-4-z!WBTS4fe~PD_gBvo(p?=Yh~+2VGI(UGyyv4mYQVQy)~VUvZJ+4x=mV7
zR(~xxcr!Y^thQ8DG9Xk%XMgfvuq{xB&w{={(~Y+0U6{zqnTs8R)gI=nrlQ%PCf0A(
z<sFUkhbO5Oof9SGjW>Ua%ez098fhXCV$lK~cE5qM#YPaq4D9hGKAtz5S;3xIoVjEl
z8(ML1^x8NZCEyg1r&*CyoZz};oWDHpxUj6Igod<m4|UZTU7%PESg6}lqydG1=Q8^m
z4q5sf@Q9F5NR)RAb^FJ>_%G+<Kjy`Me6s(K`(!&@;GGB0IT&2Hkf<6eZ9S~XYYS+!
z-n8DL^Da(+!7b+1g{spQ*>ei-`vVnb4cg>hYqm{={H^8~t8Ls{E-wXIAl|@nVhXYV
z^J)S+{FAZgw2|$Qdmd62+sBJr8>~RNo8OeXdi8wC*Oecj#lYp7R_!E2=4CG05o2aW
z|6~f9bju<7FBf^l-&=~-_NZ+)IWb5S80$5pe`-bS(0UkY7q=b0%6{E=u4EZ9_V?9m
z(XgMSQZgsS=qCm_cX|=lSbE23sPqk^XLfZCm4?a>2}?lpQ<*KEWR`+i!yU@9dfn&+
zJ`I@j4=@rQX<1uA{3+BEVU)D1Kx>Q>&{h(wm{sv2`o9%^^2Mqae43p44;>)~ih}~o
z$@XPiu9w_vi0Wv0_vA()U}uZ!p4M$oHgd~>HV8;b*PF}Jelv0U->6<_-$z6>RNna)
z8H-vbDjiO_GZ?L(cyBQ1VCoGvAen#CsNPLO1G@u#FF+V8?DA#E5N?5?J>oCdxBdN2
zz_8{Mg^Ew%{qL;$o<Oc{(}}-dD*v(ZeZw4B{J-C&`pfN!A15IWKOR`KB!W@`2lT?f
z`y7GvU4SB0|F1WgvmjvwHZ@7vXCI%)dFpd!f13Bi`!3L#3bnxs%!GrwxZ61=m3uNJ
zwh(v@zU{5-3JmgvDEX60hS_wGT_M|ikVPN7L6c`?JDp|?_Bt-8mJ!{7Ozpj7$(9LB
z^0niKzr{n2`=2EHc&Hg5CbrnYXs~kuRts>EeDI1B<jH+Ogep35(!UqPA@_(xS&YZi
zv%4T-|Lp5a@TpAM*z%G68Zdd@;-QWZsIlV9wY;vVhK!E*Qxm2psIoqc#pr>+#bzF7
z(An$PdtSGzz@o%yx;twHv~FDo@If_rwa;uiAGLjWIB+6XxELy-4JZKCI49fqKflc>
z(Vb-Fp;s5O&RPvsrJ$Aa1k@uLd*E0U<TX~CE9D#pz^rs4POTe*2tN(TTt?6UszwTG
z*j{^Knt$<@8a-&PgT?Zz93@Wo7xHbB@W>qCZtm)QuI&t9MJdqydw^!m9(BF^=ODdj
z(A&~NaoXZoy%6f|pcbkUdV;3*O6u5Wpjphu7HA5%`@hoUY0zvj&GmI{+vuuVZ<peA
zCrSpxo#eqbFk73bTJhn3tcNRgLzdn;VCS?GeGMGkU7SYh$02;@T2v+OHj`tJa_T~k
zAq!tH0J@M36)4+A%lHm9dMxOC7AS2XP0C;s<bsy2JW=r#-v)AH4lO<7P5U?HsD^Mq
z;K1z8&3SePDlCB-j?4fy+V1h@7-!(gX1>9I9xTyUfJK-sq7=ImFSrbB9ICEA`9jK{
z=o39lvrvD3)3uFt)?llQUd95Y4{R=<N6&yy{iO2RulAsdxWYFGM&ce)#>toy+~5Hn
zkg|Al^L;!5L9PW@zX$YG9$;h`$z1LWB10{_fNAGYoL&dc*lN27ihJ`NuF}4XR=d>t
z&pwgAEf`L;<JAletPGI_9jpY;(B#PYHf$r3yvQ~fy8Jm8*u_^sYh*X*(B_}la#Mzt
zIwt$TX^K~!sZRz_vq=(vn|(-eXG2n~3Y6Rv|4{Sc<lof%i;H$+P)9ZB<ve!98<-O?
zv1DMz5FpnAINS|LlvBVuYfh|qrV&!q<`10MrI+5)1uuP+7+|5NfJJj-Ses2_|4-s;
zM7T*b0zm~ishFhX$d)((ec*LYyS@exICH${;)|1{vx7rbzF3OKzoHJs&|2%cqve{C
zZ@8(flYJ64U5ho%J;xz;f`3?2>Pa8T*^Nj$m3b0P@lt#I&jr|NZlmxk7z9%_SfENX
zwf*tC7gHmk&PR2_QqX^mIes0@5{-!j%STR~7ivP?g}|qwHKnY|kErh}g|Iz@(*#cj
z1Iz78vtnC57JBqX8)~qu%^m)dQ)c?I^mcH<Cida+-)#eHYV^SCtEe_+I&xJv*s!!5
z==1<PO#NF6mrFDdREWclX<<zvbfhWvh6{}{j41T>DsI<keo^%u&_T>uG{0;UIZ7d~
z<BA$z*<qVfqjH`F-ysg%APU^jMT9*d7SXXWG9f~};H-g`lfvn)14Xz+;re557q|#7
zPJDAKF?fXr_L#x4*^#=fQ>L%Dzxo{QyPf=SIqFv8W=StoK(*%c_5kC9DLJZ;*=wck
z_)JGPRmHEokz7EZ1)N+zJjG%=j2BdGo-QjRXCPf)Fm;q2+X%Hj&kx)r@<b3*BltWj
zBN<uw;o&&U=q@60BK|h2p8x2T(}DLMp-9k2bQ*XZ_BM$4fej49b2G?kOc%q*Cdfa+
zHm1fzia7;o=wUyOrR}~!gLHXE4kV7X#1M<#Zm*9bqGH#6mZr3>-Ep%Boq0!9PfL1p
z3}XZUiIU{)Owp@5vu&|iWjGtFiyXKO+T${}f4WP=cI^17i5DcmRswtn1sK|R2H#aX
z(5;mwnfwT+d;f-#L@qK^<#gV%4By|&e@;$#S}xDY5m?R4VjqL|xilBTIW%cC-w+Ev
zzLo6{*HBLf$_wRSf#*z!Ae(t+H?8w@z^lSh;0$4seLxy~z8_vdwuuyFKLn0Ul!6OY
z;0T3Y8vnV@DnM@OMT%)Y0#~Og+brXtQVYD6?_2yvHvV7P_w~O)2{&>XuppUk1VHa_
zQ{}ReBQA<5BTqpSXd!EKg*A}j(&RN^XzwtFUuEX(mp#}Brjx`ENjr|tX6YiazimHD
zY1|JtZwN5IV<*hxAKB}>`NkXFr+3TK2eqFa{G~^lkPj_YT}~6)^(dlIm8x>GWzj{#
zcjUh2S5fY(JA!!MESnDhajJsHb8pYt;}MW(i8#YRC$}T9#@MlZo7s^O^9B&n%GY;<
zXc4YQ*J+|?SG2S_K7?s})~JtiVLVvEK~=YDSiW@bsOBszh>umARMmWbH`Y%3R~`I3
zh5lm|iZso9D2i6zTAPz#`>AeQK|b^#-jG@|S4qGyECxG;aFhq@K@9b4U2GX@d3-(5
zwn0rs8asWy!6vj8!8?7v9r>(;L<w;F<nQfT&mM7@+AuqXchqSp9x`gL?qv#U1#&!M
z3(LgNdT^{tGX#$ds}E{nLdP0_jB#ng<o$CKY=)UHEt^!_!6$pRr{s{FghkjpIU9qE
z9htJ&B28vBqG;2C-|qdR!`dVcG?lkLgwg)d<{iNX+Q&8dal8KLyFRQ7y0ItEL`D43
zKHi7{SwzGU=>F*EekcmMynV#98~<oaAJeA6MzHAy(*DsW-U_~;>0H%);Y)w?a}$Ik
z>>4qmzrJB<=bLvTv?if1N3#CNF8jwUh(O05!*baE*%|Kxdeu#et}w&@m_;ZUfq-L{
z`6IA%Dxe4cu-Q=t*dMdd1S1f=Zu0yQ*h_wpoQIMJ=oo*W1ucSZHYyU3dYgg&?tGfa
zGwg7n2)K8bICk(H=8(G1@W+MhUSb3ay_lZ=YgeUjyTF&0(deBt)G0b~>H2>IKV3-k

literal 0
HcmV?d00001

Comments

no-reply@patchew.org June 17, 2021, 1:10 p.m. UTC | #1
Patchew URL: https://patchew.org/QEMU/20210617121707.764126-1-ma.mandourr@gmail.com/



Hi,

This series seems to have some coding style problems. See output below for
more information:

Type: series
Message-id: 20210617121707.764126-1-ma.mandourr@gmail.com
Subject: [RFC PATCH v2] Add a post for the new TCG cache modelling plugin

=== TEST SCRIPT BEGIN ===
#!/bin/bash
git rev-parse base > /dev/null || exit 0
git config --local diff.renamelimit 0
git config --local diff.renames True
git config --local diff.algorithm histogram
./scripts/checkpatch.pl --mailback base..
=== TEST SCRIPT END ===

Updating 3c8cf5a9c21ff8782164d1def7f44bd888713384
Switched to a new branch 'test'
aa253ca Add a post for the new TCG cache modelling plugin

=== OUTPUT BEGIN ===
WARNING: added, moved or deleted file(s), does MAINTAINERS need updating?
#18: 
new file mode 100644

ERROR: trailing whitespace
#284: FILE: _posts/2021-06-17-tcg-cache-modelling-plugin.md:262:
+[[RFC PATCH v3 0/4] Cache TCG plugin & symbol-resolution API](https://patchew.org/QEMU/20210608040532.56449-1-ma.mandourr@gmail.com/)  $

ERROR: trailing whitespace
#285: FILE: _posts/2021-06-17-tcg-cache-modelling-plugin.md:263:
+[[RFC PATCH v3 1/4] plugins/api: expose symbol lookup to plugins](https://patchew.org/QEMU/20210608040532.56449-1-ma.mandourr@gmail.com/20210608040532.56449-2-ma.mandourr@gmail.com/)  $

ERROR: trailing whitespace
#286: FILE: _posts/2021-06-17-tcg-cache-modelling-plugin.md:264:
+[[RFC PATCH v3 2/4] plugins: Added a new cache modelling plugin.](https://patchew.org/QEMU/20210608040532.56449-1-ma.mandourr@gmail.com/20210608040532.56449-3-ma.mandourr@gmail.com/)  $

ERROR: trailing whitespace
#287: FILE: _posts/2021-06-17-tcg-cache-modelling-plugin.md:265:
+[[RFC PATCH v3 3/4] plugins/cache: Enabled cache parameterization](https://patchew.org/QEMU/20210608040532.56449-1-ma.mandourr@gmail.com/20210608040532.56449-4-ma.mandourr@gmail.com/)  $

total: 4 errors, 1 warnings, 266 lines checked

Commit aa253cab1831 (Add a post for the new TCG cache modelling plugin) has style problems, please review.  If any of these errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.
=== OUTPUT END ===

Test command exited with code: 1


The full log is available at
http://patchew.org/logs/20210617121707.764126-1-ma.mandourr@gmail.com/testing.checkpatch/?type=message.
---
Email generated automatically by Patchew [https://patchew.org/].
Please send your feedback to patchew-devel@redhat.com
diff mbox series

Patch

diff --git a/_posts/2021-06-17-tcg-cache-modelling-plugin.md b/_posts/2021-06-17-tcg-cache-modelling-plugin.md
new file mode 100644
index 0000000..5360916
--- /dev/null
+++ b/_posts/2021-06-17-tcg-cache-modelling-plugin.md
@@ -0,0 +1,266 @@ 
+---
+layout: post
+title:  "Cache Modelling TCG Plugin"
+date:   2021-06-17 06:00:00 +0200
+author: Mahmoud Mandour
+categories: [TCG plugins, GSOC]
+---
+
+TCG plugins provide means to instrument generated code for both user-mode and
+full system emulation. This includes the ability to intercept every memory
+access and instruction execution. This post introduces a new TCG plugin that's
+used to simulate configurable L1 separate instruction cache and data cache.
+
+The plugin aims to simply model different configurations of icache and dcache
+rather than simulate intricate microarchitectural details. That's because those
+details generally vary from one microarchitecture to another. Also, those
+details will be very different between TCG and real behavior. L1 caches are
+usually of low associativity, so simulating them will give us a good idea of
+what happens in real life with code that thrashes the cache.
+
+## Overview
+
+The plugin simulates how L1 user-configured caches would behave when given a
+working set defined by a program in user-mode, or system-wide working set.
+Subsequently, it logs performance statistics along with the most N
+cache-thrashing instructions.
+
+### Configurability
+
+The plugin is configurable in terms of:
+
+* icache size parameters: `arg="I=CACHE_SIZE ASSOC BLOCK_SIZE"`
+* dcache size parameters: `arg="D=CACHE_SIZE ASSOC BLOCK_SIZE"`
+* Eviction policy: `arg="evict=lru|rand|fifo"`
+* How many top-most thrashing instructions to log: `arg="limit=TOP_N"`
+* How many core caches to keep track of: `arg="cores=N_CORES"`
+
+### Multicore caching
+
+Multicore caching is achieved by having independent L1 caches for each available
+core.
+
+In __full-system emulation__, the number of available vCPUs is known to the
+plugin at plugin installation time, so separate caches are maintained for those.
+
+In __user-space emulation__, the index of the vCPU initiating a memory access
+monotonically increases and is limited with however much the kernel allows
+creating. The approach used is that we allocate a static number of caches, and
+fit all memory accesses into those cores. This is viable having more threads
+than cores will result in interleaving those threads between the available cores
+so they might thrash each other anyway.
+
+## Design and implementation
+
+### General structure
+
+A generic cache data structure, `struct Cache`, is used to model either an
+icache or dcache. For each known core, the plugin maintains an icache and a
+dcache. On a memory access coming from a core, the corresponding cache is
+interrogated.
+
+Each cache has a number of cache sets that are used to store the actual cached
+locations alongside metadata that backs eviction algorithms. The structure of a
+cache with `n` sets, and `m` blocks per sets is summarized in the following
+figure:
+
+![cache structure](/screenshots/2021-06-17-cache-structure.png)
+
+### Eviction algorithms
+
+The plugin supports three eviction algorithms:
+
+* Random eviction
+* Least recently used (LRU)
+* FIFO eviction
+
+#### Random eviction
+
+On a cache miss that requires eviction, a randomly chosen block is evicted to
+make room for the newly-fetched block.
+
+Using random eviction effectively requires no metadata for each set.
+
+#### Least recently used (LRU)
+
+For each set, a generation number is maintained that is incremented on each
+memory access and. The current generation number is assigned to the block
+currently being accessed. On a cache miss, the block with the least generation
+number is evicted.
+
+#### FIFO eviction
+
+A FIFO queue instance is maintained for each set. On a cache miss, the evicted
+block is the first-in block, and the newly-fetched block is enqueued as the
+last-in block.
+
+## Usage
+
+Now a simple example usage of the plugin is demonstrated by running a program
+that has does matrix multiplication, and how the plugin helps identify code that
+thrashes the cache.
+
+A program, `test_mm` uses the following function to carry out matrix
+multiplication:
+
+```
+void mm(int n, int m1[n][n], int m2[n][n], int res[n][n])
+{
+    for (int i = 0; i < n; i++) {
+        for (int j = 0; j < n; j++) {
+            int sum = 0;
+            for (int k = 0; k < n; k++) {
+                int op1 = m1[i][k];
+                int op2 = m2[k][j];
+                sum += op1 * op2;
+            }
+            res[i][j] = sum;
+        }
+    }
+}
+```
+
+Running `mm_test` inside QEMU using the following command:
+
+```
+./x86_64-linux-user/qemu-x86_64 $(QEMU_ARGS) \
+  -plugin ./contrib/plugins/libcache.so,arg="D=8192 4 64",arg="I=8192 4 64" \
+  -d plugin \
+  -D matmul.log \
+  ./mm_test
+```
+
+The preceding command will run QEMU and attach the plugin with the following
+configuration:
+
+* dcache: cache size = 8KBs, associativity = 4, block size = 64B.
+* icache: cache size = 8KBs, associativity = 4, block size = 64B.
+* Default eviction policy is LRU (used for both caches).
+* Default number of cores is 1.
+
+The following data is logged in `matmul.log`:
+
+```
+core #, data accesses, data misses, dmiss rate, insn accesses, insn misses, imiss rate
+0       4908419        274545          5.5933%  8002457        1005            0.0126%
+
+address, data misses, instruction
+0x4000001244 (mm), 262138, movl (%rdi, %rsi, 4), %esi
+0x400000121c (mm), 5258, movl (%rdi, %rsi, 4), %esi
+0x4000001286 (mm), 4096, movl %edi, (%r8, %rsi, 4)
+0x400000199c (main), 257, movl %edx, (%rax, %rcx, 4)
+
+...
+```
+
+We can observe two things from the logs:
+
+* The most cache-thrashing instructions belong to a symbol called `mm`, which
+    happens to be the matrix multiplication function.
+* Some array-indexing instructions are generating the greatest share of data
+    misses.
+
+`test_mm` does a bunch of other operations other than matrix multiplication.
+However, Using the plugin data, we can narrow our investigation space to `mm`,
+which happens to be generating about 98% of the overall number of misses.
+
+Now we need to find out why is the instruction at address `0x4000001224`
+thrashing the cache. Looking at the disassembly of the program, using
+`objdump -Sl test_mm`:
+
+```
+/path/to/test_mm.c:11 (discriminator 3)
+                int op2 = m2[k][j];  <- The line of code we're interested in
+    1202:	8b 75 c0             	mov    -0x40(%rbp),%esi
+    1205:	48 63 fe             	movslq %esi,%rdi
+    1208:	48 63 f2             	movslq %edx,%rsi
+    120b:	48 0f af f7          	imul   %rdi,%rsi
+    120f:	48 8d 3c b5 00 00 00 	lea    0x0(,%rsi,4),%rdi
+    1216:	00
+    1217:	48 8b 75 a8          	mov    -0x58(%rbp),%rsi
+    121b:	48 01 f7             	add    %rsi,%rdi
+    121e:	8b 75 c8             	mov    -0x38(%rbp),%esi
+    1221:	48 63 f6             	movslq %esi,%rsi
+    1224:	8b 34 b7             	mov    (%rdi,%rsi,4),%esi
+                                	^^^^^^^^^^^^^^^^^^^^^^^^^
+    1227:	89 75 d4             	mov    %esi,-0x2c(%rbp)
+```
+
+It can be seen that the most problematic instruction is associated with loading
+`m2[k][j]`. This happens because we're traversing `m2` in a column-wise order.
+So if the matrix `m2` is larger than the data cache, we end up with fetching
+blocks that we only use one integer from and not use again before getting
+evicted.
+
+A simple solution to this problem is to [transpose](https://en.wikipedia.org/wiki/Transpose)
+the second matrix and access it in a row-wise order.
+
+By editing the program to transpose `m2` before calling `mm` and run it inside
+QEMU with the plugin attached and using the same configuration as previously,
+the following data is logged in `matmul.log`:
+
+```
+core #, data accesses, data misses, dmiss rate, insn accesses, insn misses, imiss rate
+0       4998994        24235           0.4848%  8191937        1009            0.0123%
+
+address, data misses, instruction
+0x4000001244 (mm), 16447, movl (%rdi, %rsi, 4), %esi
+0x4000001359 (tran), 3994, movl (%rcx, %rdx, 4), %ecx
+0x4000001aa7 (main), 257, movl %edx, (%rax, %rcx, 4)
+0x4000001a72 (main), 257, movl %ecx, (%rax, %rdx, 4)
+
+...
+```
+
+It can be seen that a minor number of misses is generated at transposition time
+in `tran`. The rest of the matrix multiplication is carried out using the same
+procedure but to multiply `m1[i][k]` by `m2[j][k]`. So `m2` is traversed
+row-wise and hence utilized cache space much more optimally.
+
+### Multi-core caching
+
+The plugin accepts a `cores=N_CORES` argument that represents the number of
+cores that the plugin must keep track of. Memory accesses generated by excess
+threads will be served through the available core caches.
+
+An example usage of the plugin using the `cores` argument against a program that
+creates 4 threads:
+
+```
+./x86_64-linux-user/qemu-x86_64 $(QEMU_ARGS) \
+    -plugin ./contrib/plugins/libcache.so,arg="cores=4" \
+    -d plugin \
+    -D logfile \
+    ./threaded_prog
+```
+
+This reports out the following:
+
+```
+core #, data accesses, data misses, dmiss rate, insn accesses, insn misses, imiss rate
+0       76739          4195          5.411666%  242616         1555            0.6409%
+1       29029          932           3.211106%  70939          988             1.3927%
+2       6218           285           4.511835%  15702          382             2.4328%
+3       6608           297           4.411946%  16342          384             2.3498%
+sum     118594         5709          4.811139%  345599         3309            0.9575%
+
+...
+```
+
+## Conclusion
+
+By emulating simple configurations of icache and dcache we can gain insights
+about how a working set is utilizing cache memory. Simplicity is sought and
+L1 cache is emphasized since its under-utilization can be severe to the overall
+system performance.
+
+This plugin is made as part of my GSoC participation for the year 2021 under the
+mentorship of Alex Bennée.
+
+List of posted patches related to the plugin:
+
+[[RFC PATCH v3 0/4] Cache TCG plugin & symbol-resolution API](https://patchew.org/QEMU/20210608040532.56449-1-ma.mandourr@gmail.com/)  
+[[RFC PATCH v3 1/4] plugins/api: expose symbol lookup to plugins](https://patchew.org/QEMU/20210608040532.56449-1-ma.mandourr@gmail.com/20210608040532.56449-2-ma.mandourr@gmail.com/)  
+[[RFC PATCH v3 2/4] plugins: Added a new cache modelling plugin.](https://patchew.org/QEMU/20210608040532.56449-1-ma.mandourr@gmail.com/20210608040532.56449-3-ma.mandourr@gmail.com/)  
+[[RFC PATCH v3 3/4] plugins/cache: Enabled cache parameterization](https://patchew.org/QEMU/20210608040532.56449-1-ma.mandourr@gmail.com/20210608040532.56449-4-ma.mandourr@gmail.com/)  
+[[RFC PATCH v3 4/4] plugins/cache: Added FIFO and LRU eviction policies](https://patchew.org/QEMU/20210608040532.56449-1-ma.mandourr@gmail.com/20210608040532.56449-5-ma.mandourr@gmail.com/)
diff --git a/screenshots/2021-06-17-cache-structure.png b/screenshots/2021-06-17-cache-structure.png
new file mode 100644
index 0000000000000000000000000000000000000000..82a9dc07710e3d9be738d20c675c69aa90a48942