Re: overcommit stuff

Hugh Dickins wrote:

On Sat, 21 Sep 2002, Andrew Morton wrote:

quoted

Alan,

running 10,000 tiobench threads I'm showing 23 gigs of
`Commited_AS'.  Is this right?  Those pages are shared,
and if they're not PROT_WRITEable then there's no way in
which they can become unshared?   Seems to be excessively
pessimistic?

Or is 2.5 not up to date?

I don't think Alan can be held responsible for errors in the
overcommit stuff rml ported to 2.5 and I then added fixes to.

Well I'm not saying it's an error.  It may be by design.

I believe it is up to date in 2.5.

OK.
 

Committed_AS certainly errs on the pessimistic side, that's
what it's about.  How much swap do you have i.e. is 23GB
committed impossible, or just surprising to you?  Does the
number go back to what it started off from when you kill
off the tests?  How are "those pages" allocated e.g. what
mmap args?

I have 7G physical, 4G swap.

"those pages" were just used by some scruffy perl script 
running `./tiotest &' ten thousand times.  I assume it's
shared executable text.

It seems very unlikely (impossible?) that those pages will
ever become unshared.

Are they returned when the threads are killed?  Dunno - the
machine got a vists from the NMI watchdog in the scheduler
somewhere before I could tell.  Retesting...

Here's what I had when it died:

MemTotal:      7249608 kB
MemFree:          7180 kB
MemShared:           0 kB
Buffers:         29040 kB
Cached:        6879180 kB
SwapCached:      51216 kB
Active:          22672 kB
Inactive:      6950548 kB
HighTotal:     6422528 kB
HighFree:         2980 kB
LowTotal:       827080 kB
LowFree:          4200 kB
SwapTotal:     3951844 kB
SwapFree:      3829764 kB
Dirty:          658468 kB
Writeback:       10640 kB
Mapped:          57228 kB
Slab:            83188 kB
Committed_AS: 28417140 kB
PageTables:      58152 kB
ReverseMaps:     28455


nr_dirty 165433
nr_writeback 2663 
nr_pagecache 1739859
nr_page_table_pages 14538
nr_reverse_maps 28455
nr_mapped 14307
nr_slab 20802
pswpin 45
pswpout 30532
pgalloc 6671454
pgfree 6673245
pgactivate 74265
pgdeactivate 68457
pgfault 1261681
pgmajfault 714
pgscan 4640872
pgrefill 100136
pgsteal 4329474
kswapd_steal 1413013
pageoutrun 90269
allocstall 90269



       buffer_head:    25669KB    30953KB   82.92
       task_struct:    14648KB    15218KB   96.25
   radix_tree_node:    12337KB    12354KB   99.85
  ext2_inode_cache:     4058KB     4058KB  100.0 
    vm_area_struct:     2463KB     2475KB   99.52
          size-512:     1428KB     1428KB  100.0 
              filp:     1301KB     1301KB  100.0 
      dentry_cache:     1290KB     1290KB  100.0 
biovec-BIO_MAX_PAGES:      780KB      780KB  100.0 
       names_cache:      744KB      748KB   99.46
         biovec-64:      677KB      723KB   93.57
   blkdev_requests:      625KB      633KB   98.69
         size-4096:      556KB      556KB  100.0 
         pte_chain:      158KB      489KB   32.39
sgpool-MAX_PHYS_SEGMENTS:      420KB      480KB   87.50
        biovec-128:      390KB      390KB  100.0 
         size-2048:      352KB      352KB  100.0 
         size-1024:      348KB      348KB  100.0 
           size-32:      317KB      324KB   97.57
  ext3_inode_cache:      171KB      240KB   71.22
         sgpool-64:      213KB      232KB   91.93
        signal_act:      212KB      212KB  100.0
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