| Message ID | 1504893565-110166-3-git-send-email-bhanuprakash.bodireddy@intel.com |
|---|---|
| State | Accepted |
| Headers | show |
| Series | Rearrange structure members for memory efficiency. | expand |
On 09/08/2017 10:59 AM, Bhanuprakash Bodireddy wrote: > By reordering elements in dummy_packet_stream structure, sum holes Do you mean "the sum of the holes" can be reduced or do you mean "some holes" can be reduced? Same question through several of the other patches where you use the same language. Thanks, - Greg > can be reduced, thus saving a cache line. > > Before: structure size: 784, sum holes: 56, cachelines:13 > After : structure size: 768, sum holes: 40, cachelines:12 > > Signed-off-by: Bhanuprakash Bodireddy <bhanuprakash.bodireddy@intel.com> > --- > lib/netdev-dummy.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/lib/netdev-dummy.c b/lib/netdev-dummy.c > index f731af1..d888c40 100644 > --- a/lib/netdev-dummy.c > +++ b/lib/netdev-dummy.c > @@ -50,8 +50,8 @@ struct reconnect; > > struct dummy_packet_stream { > struct stream *stream; > - struct dp_packet rxbuf; > struct ovs_list txq; > + struct dp_packet rxbuf; > }; > > enum dummy_packet_conn_type { >
Hi greg, >On 09/08/2017 10:59 AM, Bhanuprakash Bodireddy wrote: >> By reordering elements in dummy_packet_stream structure, sum holes > >Do you mean "the sum of the holes" can be reduced or do you mean "some >holes" >can be reduced? In this patch series "sum of the holes" means, the sum/total of all the hole bytes in the respective structure. For example 'dummy_packet_stream' structure members are aligned below way. This structure has one hole comprising of 56 bytes. struct dummy_packet_stream { struct stream * stream; /* 0 8 */ ====> 56 bytes holes. struct dp_packet rxbuf; /* 64 704 */ struct ovs_list txq; /* 768 16 */ }; With the proposed change in this patch, the new alignment is as below struct dummy_packet_stream { struct stream * stream; /* 0 8 */ struct ovs_list txq; /* 8 16 */ ====> 40 bytes hole struct dp_packet rxbuf; /* 64 704 */ }; For all the patches, the information is added in to the commit log that shows the improvement with the proposed changes. As claimed, sum holes(bytes) are reduced from 56 to 40 in case of this patch. >> Before: structure size: 784, sum holes: 56, cachelines:13 >> After : structure size: 768, sum holes: 40, cachelines:12 > >Same question through several of the other patches where you use the same >language. In few structures there are multiple holes and 'sum holes' adds hole bytes of multiple holes In those cases. - Bhanuprakash. > >> can be reduced, thus saving a cache line. >> >> Before: structure size: 784, sum holes: 56, cachelines:13 After : >> structure size: 768, sum holes: 40, cachelines:12 >> >> Signed-off-by: Bhanuprakash Bodireddy >> <bhanuprakash.bodireddy@intel.com> >> --- >> lib/netdev-dummy.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/lib/netdev-dummy.c b/lib/netdev-dummy.c index >> f731af1..d888c40 100644 >> --- a/lib/netdev-dummy.c >> +++ b/lib/netdev-dummy.c >> @@ -50,8 +50,8 @@ struct reconnect; >> >> struct dummy_packet_stream { >> struct stream *stream; >> - struct dp_packet rxbuf; >> struct ovs_list txq; >> + struct dp_packet rxbuf; >> }; >> >> enum dummy_packet_conn_type { >>
On Fri, Sep 08, 2017 at 06:59:14PM +0100, Bhanuprakash Bodireddy wrote: > By reordering elements in dummy_packet_stream structure, sum holes > can be reduced, thus saving a cache line. > > Before: structure size: 784, sum holes: 56, cachelines:13 > After : structure size: 768, sum holes: 40, cachelines:12 > > Signed-off-by: Bhanuprakash Bodireddy <bhanuprakash.bodireddy@intel.com> I wouldn't normally bother optimizing code that is used only for testing, but the reduction in cache lines is nice, so I applied this. Thank you!
diff --git a/lib/netdev-dummy.c b/lib/netdev-dummy.c index f731af1..d888c40 100644 --- a/lib/netdev-dummy.c +++ b/lib/netdev-dummy.c @@ -50,8 +50,8 @@ struct reconnect; struct dummy_packet_stream { struct stream *stream; - struct dp_packet rxbuf; struct ovs_list txq; + struct dp_packet rxbuf; }; enum dummy_packet_conn_type {
By reordering elements in dummy_packet_stream structure, sum holes can be reduced, thus saving a cache line. Before: structure size: 784, sum holes: 56, cachelines:13 After : structure size: 768, sum holes: 40, cachelines:12 Signed-off-by: Bhanuprakash Bodireddy <bhanuprakash.bodireddy@intel.com> --- lib/netdev-dummy.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)