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Re: [PATCH nginx v2] remove ngx_cpuinfo, use sysconf or define

Joe Konno
January 16, 2020 10:40AM
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On 1/16/20 6:43 AM, Vladimir Homutov wrote:
> On Fri, Jan 03, 2020 at 02:39:29PM -0800, Joe Konno wrote:
>> # HG changeset patch
>> # User Joe Konno <joe.konno@intel.com>
>> # Date 1578075036 28800
>> # Fri Jan 03 10:10:36 2020 -0800
>> # Node ID b66ee34cea2f539bb8ce4986d6bd332f75ee06b6
>> # Parent f1720934c45be1c6469841a55d1f31fe9a630c85
>> remove ngx_cpuinfo, use sysconf or define
>>
>> Function ngx_cpuinfo() is used to (sub-optimally) determine the value of
>> ngx_cacheline_size on x86 hardware. On hardware running Linux, there may be a
>> sysconf call that correctly reports the cache line size using architecturally
>> appropriate methods-- for x86 hardware, the CPUID instruction.
>>
>> Therefore, ngx_cpuinfo is no longer needed. If said sysconf call is
>> unavailable, set ngx_cachline_size to defined NGX_CPU_CACHE_LINE, the value of
>> which is determined at configure time.
>>
>> Signed-off-by: Joe Konno <joe.konno@intel.com>
>>
>> diff -r f1720934c45b -r b66ee34cea2f auto/sources
>> --- a/auto/sources Fri Dec 27 19:43:01 2019 +0300
>> +++ b/auto/sources Fri Jan 03 10:10:36 2020 -0800
>> @@ -71,7 +71,6 @@
>> src/core/ngx_cycle.c \
>> src/core/ngx_spinlock.c \
>> src/core/ngx_rwlock.c \
>> - src/core/ngx_cpuinfo.c \
>> src/core/ngx_conf_file.c \
>> src/core/ngx_module.c \
>> src/core/ngx_resolver.c \
>> diff -r f1720934c45b -r b66ee34cea2f src/core/ngx_core.h
>> --- a/src/core/ngx_core.h Fri Dec 27 19:43:01 2019 +0300
>> +++ b/src/core/ngx_core.h Fri Jan 03 10:10:36 2020 -0800
>> @@ -102,7 +102,6 @@
>> #define ngx_max(val1, val2) ((val1 < val2) ? (val2) : (val1))
>> #define ngx_min(val1, val2) ((val1 > val2) ? (val2) : (val1))
>>
>> -void ngx_cpuinfo(void);
>>
>> #if (NGX_HAVE_OPENAT)
>> #define NGX_DISABLE_SYMLINKS_OFF 0
>> diff -r f1720934c45b -r b66ee34cea2f src/core/ngx_cpuinfo.c
>> --- a/src/core/ngx_cpuinfo.c Fri Dec 27 19:43:01 2019 +0300
>> +++ /dev/null Thu Jan 01 00:00:00 1970 +0000
>> @@ -1,139 +0,0 @@
>> -
>> -/*
>> - * Copyright (C) Igor Sysoev
>> - * Copyright (C) Nginx, Inc.
>> - */
>> -
>> -
>> -#include <ngx_config.h>
>> -#include <ngx_core.h>
>> -
>> -
>> -#if (( __i386__ || __amd64__ ) && ( __GNUC__ || __INTEL_COMPILER ))
>> -
>> -
>> -static ngx_inline void ngx_cpuid(uint32_t i, uint32_t *buf);
>> -
>> -
>> -#if ( __i386__ )
>> -
>> -static ngx_inline void
>> -ngx_cpuid(uint32_t i, uint32_t *buf)
>> -{
>> -
>> - /*
>> - * we could not use %ebx as output parameter if gcc builds PIC,
>> - * and we could not save %ebx on stack, because %esp is used,
>> - * when the -fomit-frame-pointer optimization is specified.
>> - */
>> -
>> - __asm__ (
>> -
>> - " mov %%ebx, %%esi; "
>> -
>> - " cpuid; "
>> - " mov %%eax, (%1); "
>> - " mov %%ebx, 4(%1); "
>> - " mov %%edx, 8(%1); "
>> - " mov %%ecx, 12(%1); "
>> -
>> - " mov %%esi, %%ebx; "
>> -
>> - : : "a" (i), "D" (buf) : "ecx", "edx", "esi", "memory" );
>> -}
>> -
>> -
>> -#else /* __amd64__ */
>> -
>> -
>> -static ngx_inline void
>> -ngx_cpuid(uint32_t i, uint32_t *buf)
>> -{
>> - uint32_t eax, ebx, ecx, edx;
>> -
>> - __asm__ (
>> -
>> - "cpuid"
>> -
>> - : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx) : "a" (i) );
>> -
>> - buf[0] = eax;
>> - buf[1] = ebx;
>> - buf[2] = edx;
>> - buf[3] = ecx;
>> -}
>> -
>> -
>> -#endif
>> -
>> -
>> -/* auto detect the L2 cache line size of modern and widespread CPUs */
>> -
>> -void
>> -ngx_cpuinfo(void)
>> -{
>> - u_char *vendor;
>> - uint32_t vbuf[5], cpu[4], model;
>> -
>> - vbuf[0] = 0;
>> - vbuf[1] = 0;
>> - vbuf[2] = 0;
>> - vbuf[3] = 0;
>> - vbuf[4] = 0;
>> -
>> - ngx_cpuid(0, vbuf);
>> -
>> - vendor = (u_char *) &vbuf[1];
>> -
>> - if (vbuf[0] == 0) {
>> - return;
>> - }
>> -
>> - ngx_cpuid(1, cpu);
>> -
>> - if (ngx_strcmp(vendor, "GenuineIntel") == 0) {
>> -
>> - switch ((cpu[0] & 0xf00) >> 8) {
>> -
>> - /* Pentium */
>> - case 5:
>> - ngx_cacheline_size = 32;
>> - break;
>> -
>> - /* Pentium Pro, II, III */
>> - case 6:
>> - ngx_cacheline_size = 32;
>> -
>> - model = ((cpu[0] & 0xf0000) >> 8) | (cpu[0] & 0xf0);
>> -
>> - if (model >= 0xd0) {
>> - /* Intel Core, Core 2, Atom */
>> - ngx_cacheline_size = 64;
>> - }
>> -
>> - break;
>> -
>> - /*
>> - * Pentium 4, although its cache line size is 64 bytes,
>> - * it prefetches up to two cache lines during memory read
>> - */
>> - case 15:
>> - ngx_cacheline_size = 128;
>> - break;
>> - }
>> -
>> - } else if (ngx_strcmp(vendor, "AuthenticAMD") == 0) {
>> - ngx_cacheline_size = 64;
>> - }
>> -}
>> -
>> -#else
>> -
>> -
>> -void
>> -ngx_cpuinfo(void)
>> -{
>> -}
>> -
>> -
>> -#endif
>> diff -r f1720934c45b -r b66ee34cea2f src/os/unix/ngx_posix_init.c
>> --- a/src/os/unix/ngx_posix_init.c Fri Dec 27 19:43:01 2019 +0300
>> +++ b/src/os/unix/ngx_posix_init.c Fri Jan 03 10:10:36 2020 -0800
>> @@ -51,10 +51,20 @@
>> }
>>
>> ngx_pagesize = getpagesize();
>> - ngx_cacheline_size = NGX_CPU_CACHE_LINE;
>>
>> for (n = ngx_pagesize; n >>= 1; ngx_pagesize_shift++) { /* void */ }
>>
>> +#if (NGX_HAVE_LEVEL1_DCACHE_LINESIZE)
>> + size = sysconf(_SC_LEVEL1_DCACHE_LINESIZE);
>> + if (size > 0) {
>> + ngx_cacheline_size = size;
>> + } else {
>> + ngx_cacheline_size = NGX_CPU_CACHE_LINE;
>> + }
>> +#else
>> + ngx_cacheline_size = NGX_CPU_CACHE_LINE;
>> +#endif
>> +
>> #if (NGX_HAVE_SC_NPROCESSORS_ONLN)
>> if (ngx_ncpu == 0) {
>> ngx_ncpu = sysconf(_SC_NPROCESSORS_ONLN);
>> @@ -65,15 +75,6 @@
>> ngx_ncpu = 1;
>> }
>>
>> -#if (NGX_HAVE_LEVEL1_DCACHE_LINESIZE)
>> - size = sysconf(_SC_LEVEL1_DCACHE_LINESIZE);
>> - if (size > 0) {
>> - ngx_cacheline_size = size;
>> - }
>> -#endif
>> -
>> - ngx_cpuinfo();
>> -
>> if (getrlimit(RLIMIT_NOFILE, &rlmt) == -1) {
>> ngx_log_error(NGX_LOG_ALERT, log, errno,
>> "getrlimit(RLIMIT_NOFILE) failed");
>>
>
> Thank you for sharing!
>
> Removing ngx_cpuinfo() doesn't look correct: by doing this you deprive
> non-Linux systems (BSDs, windows and some others) support for CPU detection.

Valid point. Thanks for reviewing.

v1 of that patch used CPUID to retrieve the cache line size directly
from H/W:

http://mailman.nginx.org/pipermail/nginx-devel/2019-December/012853.html
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Subject Author Views Posted

[PATCH] ngx_cpuinfo: x86: CPUID to set ngx_cacheline_size

Joe Konno 179 December 23, 2019 01:42PM

[PATCH nginx v2] remove ngx_cpuinfo, use sysconf or define

Joe Konno 46 January 03, 2020 05:40PM

Re: [PATCH nginx v2] remove ngx_cpuinfo, use sysconf or define

Vladimir Homutov 24 January 16, 2020 09:44AM

Re: [PATCH nginx v2] remove ngx_cpuinfo, use sysconf or define

Joe Konno 24 January 16, 2020 10:40AM

Re: [PATCH nginx v2] remove ngx_cpuinfo, use sysconf or define

Vladimir Homutov 26 January 16, 2020 10:48AM

Re: [PATCH nginx v2] remove ngx_cpuinfo, use sysconf or define

Joe Konno 50 January 16, 2020 03:44PM



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