| Message ID | 50A23EB0.1060808@gmail.com |
|---|---|
| State | Awaiting Upstream, archived |
| Delegated to: | David Miller |
| Headers | show |
On Tue, Nov 13, 2012 at 08:36:00PM +0800, Shan Wei wrote: > Steffen Klassert said, at 2012/11/13 18:48: > > > > Ok, so please add a commit message to describe your changes. > > > > Thanks. > > > > [PATCH v5] net: xfrm: use __this_cpu_read per-cpu helper > > this_cpu_ptr/this_cpu_read is faster than per_cpu_ptr(p, smp_processor_id()) > and can reduce memory accesses. > The latter helper needs to find the offset for current cpu, > and needs more assembler instructions which objdump shows in following. > > this_cpu_ptr relocates and address. this_cpu_read() relocates the address > and performs the fetch. this_cpu_read() saves you more instructions > since it can do the relocation and the fetch in one instruction. > > per_cpu_ptr(p, smp_processor_id())： > 1e: 65 8b 04 25 00 00 00 00 mov %gs:0x0,%eax > 26: 48 98 cltq > 28: 31 f6 xor %esi,%esi > 2a: 48 c7 c7 00 00 00 00 mov $0x0,%rdi > 31: 48 8b 04 c5 00 00 00 00 mov 0x0(,%rax,8),%rax > 39: c7 44 10 04 14 00 00 00 movl $0x14,0x4(%rax,%rdx,1) > > this_cpu_ptr(p) > 1e: 65 48 03 14 25 00 00 00 00 add %gs:0x0,%rdx > 27: 31 f6 xor %esi,%esi > 29: c7 42 04 14 00 00 00 movl $0x14,0x4(%rdx) > 30: 48 c7 c7 00 00 00 00 mov $0x0,%rdi > > Signed-off-by: Shan Wei <davidshan@tencent.com> Applied to ipsec-next, thanks! -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/xfrm/xfrm_ipcomp.c b/net/xfrm/xfrm_ipcomp.c index e5246fb..2906d52 100644 --- a/net/xfrm/xfrm_ipcomp.c +++ b/net/xfrm/xfrm_ipcomp.c @@ -276,18 +276,16 @@ static struct crypto_comp * __percpu *ipcomp_alloc_tfms(const char *alg_name) struct crypto_comp * __percpu *tfms; int cpu; - /* This can be any valid CPU ID so we don't need locking. */ - cpu = raw_smp_processor_id(); list_for_each_entry(pos, &ipcomp_tfms_list, list) { struct crypto_comp *tfm; - tfms = pos->tfms; - tfm = *per_cpu_ptr(tfms, cpu); + /* This can be any valid CPU ID so we don't need locking. */ + tfm = __this_cpu_read(*pos->tfms); if (!strcmp(crypto_comp_name(tfm), alg_name)) { pos->users++; - return tfms; + return pos->tfms; } }