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Date: Thu, 18 Aug 2016 18:42:40 +0200
From: Michal Hocko <mhocko@...nel.org>
To: Joe Perches <joe@...ches.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
LKML <linux-kernel@...r.kernel.org>, Jann Horn <jann@...jh.net>
Subject: Re: [PATCH] proc, smaps: reduce printing overhead
On Thu 18-08-16 08:23:30, Joe Perches wrote:
> On Thu, 2016-08-18 at 16:58 +0200, Michal Hocko wrote:
> > On Thu 18-08-16 07:46:03, Joe Perches wrote:
> > >
> > > On Thu, 2016-08-18 at 16:41 +0200, Michal Hocko wrote:
> > > >
> > > > On Thu 18-08-16 16:26:16, Michal Hocko wrote:
> > > > >
> > > > > b) doesn't it try to be overly clever when doing that in the caller
> > > > > doesn't cost all that much? Sure you can save few bytes in the spaces
> > > > > but then I would just argue to use \t rather than fixed string length.
> > > > ohh, I misread the code. It tries to emulate the width formater. But is
> > > > this really necessary? Do we know about any tools doing a fixed string
> > > > parsing?
> > > I don't, but it's proc and all the output formatting
> > > shouldn't be changed.
> > >
> > > Appended to is generally OK, but whitespace changed is
> > > not good.
> > OK fair enough, I will
> > - seq_write(m, s, 16);
> > + seq_puts(m, s);
> >
> > because smaps needs more than 16 chars and export it in
> > fs/proc/internal.h
> >
> > will retest and repost.
>
> The shift in the meminfo case uses PAGE_SHIFT too.
OK, I have missed that part as well. So I have to do turn all the values
into page units from bytes just to let the function turn them into kB.
Sigh...
But anyway, I have done basically a copy of your show_val_kb and run
on top of the current linux-next and while the base is giving me the
comparable results to my mmomt based testing:
Command being timed: "awk /^Rss/{rss+=$2} /^Pss/{pss+=$2} END {printf "rss:%d pss:%d\n", rss, pss} /proc/3021/smaps"
User time (seconds): 0.00
System time (seconds): 0.44
Percent of CPU this job got: 99%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.45
The patch on top (below) is eating actually more system time which is
more than unexpected to me:
Command being timed: "awk /^Rss/{rss+=$2} /^Pss/{pss+=$2} END {printf "rss:%d pss:%d\n", rss, pss} /proc/3048/smaps"
User time (seconds): 0.00
System time (seconds): 0.50
Percent of CPU this job got: 99%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.50
and perf says
21.65% awk [kernel.kallsyms] [k] seq_puts
8.41% awk [kernel.kallsyms] [k] seq_write
4.64% awk [kernel.kallsyms] [k] vsnprintf
4.20% awk [kernel.kallsyms] [k] format_decode
3.37% awk [kernel.kallsyms] [k] show_smap
2.15% awk [kernel.kallsyms] [k] lock_acquire
2.05% awk [kernel.kallsyms] [k] num_to_str
2.05% awk [kernel.kallsyms] [k] print_name_value_kb
1.76% awk [kernel.kallsyms] [k] shmem_mapping
1.61% awk [kernel.kallsyms] [k] number
The results were slightly better when I dropped the alignment thingy
and returned back to seq_put_decimal_ull but it was still sys in range
0.46-0.48. So I though I just made some mistake in my previous measuring
but getting back to my testing kernel based on the mmotm tree it all
gets back to sys 0.40-0.41 while the base mmotm was 0.44-0.48.
I didn't get to compare perf profiles closely but I do not see anything
really outstanding there at the first glance. I will probably not pursue
this anymore as I do not have enough time to debug this any further
and the results do not seem so convincing with the linux-next anymore.
Maybe measuring this on the bare metal will lead to different results
(I was using kvm virt. machine). Or maybe I just made a stupid mistake
somewhere...
---
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 187d84ef9de9..eebebbc12c67 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -721,6 +721,23 @@ void __weak arch_show_smap(struct seq_file *m, struct vm_area_struct *vma)
{
}
+static void print_name_value_kb(struct seq_file *m, const char *name, unsigned long val)
+{
+ static const char blanks[7] = {' ', ' ', ' ', ' ',' ', ' ', ' '};
+ char v[32];
+ int len;
+
+ seq_puts(m, name);
+ len = num_to_str(v, sizeof(v), val >> 10);
+ if (len > 0) {
+ if (len < 8)
+ seq_write(m, blanks, 8 - len);
+
+ seq_write(m, v, len);
+ }
+ seq_puts(m, " kB\n");
+}
+
static int show_smap(struct seq_file *m, void *v, int is_pid)
{
struct vm_area_struct *vma = v;
@@ -765,45 +782,25 @@ static int show_smap(struct seq_file *m, void *v, int is_pid)
show_map_vma(m, vma, is_pid);
- seq_printf(m,
- "Size: %8lu kB\n"
- "Rss: %8lu kB\n"
- "Pss: %8lu kB\n"
- "Shared_Clean: %8lu kB\n"
- "Shared_Dirty: %8lu kB\n"
- "Private_Clean: %8lu kB\n"
- "Private_Dirty: %8lu kB\n"
- "Referenced: %8lu kB\n"
- "Anonymous: %8lu kB\n"
- "AnonHugePages: %8lu kB\n"
- "ShmemPmdMapped: %8lu kB\n"
- "Shared_Hugetlb: %8lu kB\n"
- "Private_Hugetlb: %7lu kB\n"
- "Swap: %8lu kB\n"
- "SwapPss: %8lu kB\n"
- "KernelPageSize: %8lu kB\n"
- "MMUPageSize: %8lu kB\n"
- "Locked: %8lu kB\n",
- (vma->vm_end - vma->vm_start) >> 10,
- mss.resident >> 10,
- (unsigned long)(mss.pss >> (10 + PSS_SHIFT)),
- mss.shared_clean >> 10,
- mss.shared_dirty >> 10,
- mss.private_clean >> 10,
- mss.private_dirty >> 10,
- mss.referenced >> 10,
- mss.anonymous >> 10,
- mss.anonymous_thp >> 10,
- mss.shmem_thp >> 10,
- mss.shared_hugetlb >> 10,
- mss.private_hugetlb >> 10,
- mss.swap >> 10,
- (unsigned long)(mss.swap_pss >> (10 + PSS_SHIFT)),
- vma_kernel_pagesize(vma) >> 10,
- vma_mmu_pagesize(vma) >> 10,
- (vma->vm_flags & VM_LOCKED) ?
- (unsigned long)(mss.pss >> (10 + PSS_SHIFT)) : 0);
-
+ print_name_value_kb(m, "Size: ", vma->vm_end - vma->vm_start);
+ print_name_value_kb(m, "Rss: ", mss.resident);
+ print_name_value_kb(m, "Pss: ", (unsigned long)(mss.pss >> PSS_SHIFT));
+ print_name_value_kb(m, "Shared_Clean: ", mss.shared_clean);
+ print_name_value_kb(m, "Shared_Dirty: ", mss.shared_dirty);
+ print_name_value_kb(m, "Private_Clean: ", mss.private_clean);
+ print_name_value_kb(m, "Private_Dirty: ", mss.private_dirty);
+ print_name_value_kb(m, "Referenced: ", mss.referenced);
+ print_name_value_kb(m, "Anonymous: ", mss.anonymous);
+ print_name_value_kb(m, "AnonHugePages: ", mss.anonymous_thp);
+ print_name_value_kb(m, "ShmemPmdMapped: ", mss.shmem_thp);
+ print_name_value_kb(m, "Shared_Hugetlb: ", mss.shared_hugetlb);
+ print_name_value_kb(m, "Private_Hugetlb: ", mss.private_hugetlb);
+ print_name_value_kb(m, "Swap: ", mss.swap);
+ print_name_value_kb(m, "SwapPss: ", (unsigned long)(mss.swap_pss >> PSS_SHIFT));
+ print_name_value_kb(m, "KernelPageSize: ", vma_kernel_pagesize(vma));
+ print_name_value_kb(m, "MMUPageSize: ", vma_mmu_pagesize(vma));
+ print_name_value_kb(m, "Locked: ", (vma->vm_flags & VM_LOCKED) ?
+ (unsigned long)(mss.pss >> PSS_SHIFT) : 0);
arch_show_smap(m, vma);
show_smap_vma_flags(m, vma);
m_cache_vma(m, vma);
--
Michal Hocko
SUSE Labs
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