On 02/07/2018 10:07, Chris Wilson wrote:
sysinfo() doesn't include all reclaimable memory. In particular it
excludes the majority of global_node_page_state(NR_FILE_PAGES),
reclaimable pages that are a copy of on-disk files It seems the only way
to obtain this counter is by parsing /proc/meminfo. For comparison,
check vm_enough_memory() which includes NR_FILE_PAGES as available
(sadly there's no way to call vm_enough_memory() directly either!)
v2: Pay attention to what one writes.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
lib/intel_os.c | 36 +++++++++++++++++++++++++++++++-----
1 file changed, 31 insertions(+), 5 deletions(-)
diff --git a/lib/intel_os.c b/lib/intel_os.c
index 885ffdcec..5bd18fc52 100644
--- a/lib/intel_os.c
+++ b/lib/intel_os.c
@@ -84,6 +84,18 @@ intel_get_total_ram_mb(void)
return retval / (1024*1024);
}
+static uint64_t get_meminfo(const char *info, const char *tag)
+{
+ const char *str;
+ unsigned long val;
+
+ str = strstr(info, tag);
+ if (str && sscanf(str + strlen(tag), " %lu", &val) == 1)
+ return (uint64_t)val << 10;
+
+ return 0;
Might be safer to assert format was as expected and keywords we expect
are there, rather than silently return zero.
+}
+
/**
* intel_get_avail_ram_mb:
*
@@ -96,17 +108,31 @@ intel_get_avail_ram_mb(void)
uint64_t retval;
#ifdef HAVE_STRUCT_SYSINFO_TOTALRAM /* Linux */
- struct sysinfo sysinf;
+ char *info;
int fd;
fd = drm_open_driver(DRIVER_INTEL);
intel_purge_vm_caches(fd);
close(fd);
- igt_assert(sysinfo(&sysinf) == 0);
- retval = sysinf.freeram;
- retval += min(sysinf.freeswap, sysinf.bufferram);
- retval *= sysinf.mem_unit;
+ fd = open("/proc", O_RDONLY);
+ info = igt_sysfs_get(fd, "meminfo");
+ close(fd);
+
+ if (info) {
+ retval = get_meminfo(info, "MemAvailable: ");
+ retval += get_meminfo(info, "Buffers: ");
+ retval += get_meminfo(info, "Cached: ");
+ retval += get_meminfo(info, "SwapCached: ");
I think it would be more robust to have no trailing space in tag strings.
+ free(info);
+ } else {
+ struct sysinfo sysinf;
+
+ igt_assert(sysinfo(&sysinf) == 0);
+ retval = sysinf.freeram;
+ retval += min(sysinf.freeswap, sysinf.bufferram);
+ retval *= sysinf.mem_unit;
+ }
Not sure it is worth keeping this path - will we ever not have
/proc/meminfo?
#elif defined(_SC_PAGESIZE) && defined(_SC_AVPHYS_PAGES) /* Solaris */
long pagesize, npages;
Google agrees with you that sysinfo indeed has this limitation. So in
general no complaints.
One tiny detail might be that this would now return a too large value -
doesn't count that it should not swap out itself when thinking about
free memory. But I don't think that is for this level of API to concern
with - it is definitely way more correct to report page cache.
Regards,
Tvrtko
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