Re: [PATCH 1/2] perf/powerpc/hv-24x7: Use per-cpu page buffer
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2014-12-10 09:09:13
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lkml
On Tue, 2014-12-09 at 23:06 -0800, Sukadev Bhattiprolu wrote:
quoted hunk ↗ jump to hunk
From 470c16c8955672103a9529c78dffbb239e9e27b8 Mon Sep 17 00:00:00 2001 From: Sukadev Bhattiprolu <redacted> Date: Tue, 9 Dec 2014 22:17:46 -0500 Subject: [PATCH 1/2] perf/poweprc/hv-24x7: Use per-cpu page bufferdiff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c index dba3408..18e1f49 100644 --- a/arch/powerpc/perf/hv-24x7.c +++ b/arch/powerpc/perf/hv-24x7.c@@ -217,11 +217,14 @@ static bool is_physical_domain(int domain) domain == HV_24X7_PERF_DOMAIN_PHYSICAL_CORE; } +DEFINE_PER_CPU(char, hv_24x7_reqb[4096]); +DEFINE_PER_CPU(char, hv_24x7_resb[4096]);
Do we need it to be 4K aligned also? I would guess so. Rather than declaring these as char arrays and then casting below, can you pull the struct definitions up and then declare the per cpu variables with the proper type.
quoted hunk ↗ jump to hunk
static unsigned long single_24x7_request(u8 domain, u32 offset, u16 ix, u16 lpar, u64 *res, bool success_expected) { - unsigned long ret = -ENOMEM; + unsigned long ret; /* * request_buffer and result_buffer are not required to be 4k aligned,@@ -243,13 +246,11 @@ static unsigned long single_24x7_request(u8 domain, u32 offset, u16 ix, BUILD_BUG_ON(sizeof(*request_buffer) > 4096); BUILD_BUG_ON(sizeof(*result_buffer) > 4096); - request_buffer = kmem_cache_zalloc(hv_page_cache, GFP_USER); - if (!request_buffer) - goto out; + request_buffer = (void *)get_cpu_var(hv_24x7_reqb); + result_buffer = (void *)get_cpu_var(hv_24x7_resb); - result_buffer = kmem_cache_zalloc(hv_page_cache, GFP_USER); - if (!result_buffer) - goto out_free_request_buffer; + memset(request_buffer, 0, 4096); + memset(result_buffer, 0, 4096);
Do we have to memset them? That's not going to speed things up. cheers