Re: [BUG] Error reading multiple large files

Re: [BUG] Error reading multiple large files

[Roy Sigurd Karlsbakk]

> you really should try akpm's "[patch, CFT] improved disk read latency"
> patch.  it sounds almost perfect for your application.

hi

It seemed like it helped first, but after a while, some 99 processes went
Defunct, and locked. After this, the total 'bi' as reported from vmstat
went down to ~ 900kB per sec

What should I do? Run Windoze?

--
Roy Sigurd Karlsbakk, MCSE, MCNE, CLS, LCA

Computers are like air conditioners.
They stop working when you open Windows.

Re: [BUG] Error reading multiple large files

[Jens Axboe]

On Wed, Jan 09 2002, Roy Sigurd Karlsbakk wrote:
> > you really should try akpm's "[patch, CFT] improved disk read latency"
> > patch.  it sounds almost perfect for your application.
> 
> hi
> 
> It seemed like it helped first, but after a while, some 99 processes went
> Defunct, and locked. After this, the total 'bi' as reported from vmstat
> went down to ~ 900kB per sec

Bad news for Andrew's patch, however I really don't think it would have
helped you much in the first place. The problem seems to be down to
loosing read-ahead when cache ends up eating all of available memory,
I've seen this effect myself too. Maybe the vm needs to be more
aggressive about tossing out pages when this happens, I'm quite sure
that would help tremendously for this workload.

-- 
Jens Axboe

Re: [BUG] Error reading multiple large files

[Roy Sigurd Karlsbakk]

> > It seemed like it helped first, but after a while, some 99 processes went
> > Defunct, and locked. After this, the total 'bi' as reported from vmstat
> > went down to ~ 900kB per sec
>
> Bad news for Andrew's patch, however I really don't think it would have
> helped you much in the first place. The problem seems to be down to
> loosing read-ahead when cache ends up eating all of available memory,
> I've seen this effect myself too. Maybe the vm needs to be more
> aggressive about tossing out pages when this happens, I'm quite sure
> that would help tremendously for this workload.

Thanks for answering. I'm really close to giving up and have already
started testing on *BSD unices.

It seems reasonable if that (tossing old pages) could be the problem.

Thanks, guys

--
Roy Sigurd Karlsbakk, MCSE, MCNE, CLS, LCA

Computers are like air conditioners.
They stop working when you open Windows.

Re: [BUG] Error reading multiple large files (analyzing... ?)

[Roy Sigurd Karlsbakk]

> Bad news for Andrew's patch, however I really don't think it would have
> helped you much in the first place. The problem seems to be down to
> loosing read-ahead when cache ends up eating all of available memory,
> I've seen this effect myself too. Maybe the vm needs to be more
> aggressive about tossing out pages when this happens, I'm quite sure
> that would help tremendously for this workload.

I just wanted to tell I've tried this on 2.4.9 (as a beleive is before the new
vm came in)with the same result. What's interesting, is that the error shows up,
not at the time the buffer memory is used, but seemingly after it's been used
_twice_ (or three times?).

Can this help anyone getting a clue what the h... happens here?

The computer's got 1GB memory. Highmem is disabled.

roy

vmstat output:
---
   procs                      memory    swap          io     system         cpu
 r  b  w   swpd   free   buff  cache  si  so    bi    bo   in    cs  us  sy  id
 0 100  0      0 511448   2492 244828   0   0 29938     0 1970   882   1  15  84
 0 100  0      0 440652   2516 313320   0   0 34258     0  407   338   1   6  93
 0 100  0      0 367956   2608 383576   0   0 35164     0  433   355   0   6  93
 0 100  0      0 298868   2696 450348   0   0 34382     0  414   363   1   6  93
 0 100  0      0 229452   2876 517344   0   0 32620     0 1037   560   1  12  87
 0 100  0      0 158716   3040 585636   0   0 34238     0  429   353   0   7  93
 0 100  0      0  88372   3156 653596   0   0 34034     0  436   278   0   7  92
 0 100  0      0  19068   3204 720616   0   0 33550     0  444   219   0   9  91
 0 100  0      0   2560   3284 737580   0   0 38622     0  468  1282   1  24  75
 0 100  0      0   2768   3360 737340   0   0 36626     0  664  2763   1  23  76
 0 100  0      0   2816   3440 737120   0   0 35466     0  559  2262   1  18  81
 0 100  0      0   3056   3500 736716   0   0 36492     0  486  1963   1  19  80
 0 100  0      0   3056   3548 736708   0   0 39018     0  543  2101   1  14  86
 0 100  0      0   3056   3628 736508   0   0 36868     0  875  1707   1  17  83
 0 100  0      0   2856   3688 736728   0   0 29708     0  493  1793   0  14  86
 0 100  0      0   3056   3716 736448   0   0 32000    34  526  1888   1  16  83
 0 100  0      0   3056   3740 736448   0   0 29102     0  563  1400   1  14  85
 0 100  0      0   3056   3764 736396   0   0 24992     0  618  1266   1   9  90
 0 100  0      0   3056   3780 736384   0   0 24678     0  671  1184   1  13  86
 2  98  0      0   3004   3792 736464   0   0 20288     0 1071  1537   1  16  82
 0 100  0      0   3008   3804 736376   0   0 14620     0  932   812   0  10  90
 0 100  0      0   3008   3804 736372   0   0  6776     0 1122   726   1   8  90
 0 100  0      0   3056   3812 736328   0   0  4326     0 1195   714   0   6  93
 0 100  0      0   3056   3812 736352   0   0  1826     0 1142   623   0   4  96
 0 100  0      0   3056   3812 736364   0   0  1026     0 1093   563   0   5  95
 0 100  0      0   3056   3812 736364   0   0  1058     0 1114   567   1   3  96
 0 100  0      0   3056   3812 736360   0   0  1066     0 1124   586   0   3  96
 0 100  0      0   3056   3816 736356   0   0  2474     0 1112   574   0   4  96


--
Roy Sigurd Karlsbakk, MCSE, MCNE, CLS, LCA

Computers are like air conditioners.
They stop working when you open Windows.

Re: [BUG] Error reading multiple large files

[Rik van Riel]

On Wed, 9 Jan 2002, Roy Sigurd Karlsbakk wrote:

> > you really should try akpm's "[patch, CFT] improved disk read latency"
> > patch.  it sounds almost perfect for your application.

> It seemed like it helped first, but after a while, some 99 processes
> went Defunct, and locked. After this, the total 'bi' as reported from
> vmstat went down to ~ 900kB per sec
>
> What should I do?

I've done a little bit of low memory testing with my -rmap
VM patch, the system seems to be working just fine with 8MB
of RAM ...

If you have the time, could you try the following patch ?

	http://surriel.com/patches/2.4/2.4.17-rmap-11a


regards,

Rik
-- 
"Linux holds advantages over the single-vendor commercial OS"
    -- Microsoft's "Competing with Linux" document

http://www.surriel.com/		http://distro.conectiva.com/

Re: [BUG] Error reading multiple large files

[Roy Sigurd Karlsbakk]

> I've done a little bit of low memory testing with my -rmap
> VM patch, the system seems to be working just fine with 8MB
> of RAM ...
>
> If you have the time, could you try the following patch ?
>
> 	http://surriel.com/patches/2.4/2.4.17-rmap-11a

Do you think this is the case? I've 1GB memory in the box (no highmem)

--
Roy Sigurd Karlsbakk, MCSE, MCNE, CLS, LCA

Computers are like air conditioners.
They stop working when you open Windows.

Re: [BUG] Error reading multiple large files :-)

[Roy Sigurd Karlsbakk]

Thanks, guys!

This actually solved the problem, and even gave me a little increase in
read speed as a bonus.

Is this somehow planned for a 2.4 merge?

roy

On Wed, 9 Jan 2002, Rik van Riel wrote:

> On Wed, 9 Jan 2002, Roy Sigurd Karlsbakk wrote:
>
> > > you really should try akpm's "[patch, CFT] improved disk read latency"
> > > patch.  it sounds almost perfect for your application.
>
> > It seemed like it helped first, but after a while, some 99 processes
> > went Defunct, and locked. After this, the total 'bi' as reported from
> > vmstat went down to ~ 900kB per sec
> >
> > What should I do?
>
> I've done a little bit of low memory testing with my -rmap
> VM patch, the system seems to be working just fine with 8MB
> of RAM ...
>
> If you have the time, could you try the following patch ?
>
> 	http://surriel.com/patches/2.4/2.4.17-rmap-11a
>
>
> regards,
>
> Rik
> --
> "Linux holds advantages over the single-vendor commercial OS"
>     -- Microsoft's "Competing with Linux" document
>
> http://www.surriel.com/		http://distro.conectiva.com/
>

--
Roy Sigurd Karlsbakk, MCSE, MCNE, CLS, LCA

Computers are like air conditioners.
They stop working when you open Windows.

Re: [BUG] Error reading multiple large files

[MrChuoi]

On Wednesday 09 January 2002 08:56 pm, Roy Sigurd Karlsbakk wrote:
> > you really should try akpm's "[patch, CFT] improved disk read latency"
> > patch.  it sounds almost perfect for your application.
>
> hi
>
> It seemed like it helped first, but after a while, some 99 processes went
> Defunct, and locked. After this, the total 'bi' as reported from vmstat
> went down to ~ 900kB per sec
>
> What should I do? Run Windoze?
Windoze can do it better ? :-\

[BUG] Error reading multiple large files

[Roy Sigurd Karlsbakk]

Hi all

I've sent this before, but as far as I can see, nothing's changed.

I'm having problems reading multiple large files at once. Reading 100 1GB
files at once.

What happens is, when the buffer cache gets filled up, it all stalls, and
transfer speed drops from 40-50 MB/s to a mere 2MB/s.

This has been tested on all versions from 2.4.16-2.4.18-pre1.

I've been testing Tux, Khttpd, apache 1.3.22, Apache 2, thttpd, cp and
dd to verify the bug.

Please help!

roy

--
Roy Sigurd Karlsbakk, MCSE, MCNE, CLS, LCA

Computers are like air conditioners.
They stop working when you open Windows.

Re: [BUG] Error reading multiple large files

[Marcelo Tosatti]

Roy,

I suspect this is a use-once effect.

Could you please try http://surriel.com/patches/2.4/2.4.17-pre8-2ndchance
? 

Thanks

On Mon, 7 Jan 2002, Roy Sigurd Karlsbakk wrote:

> Hi all
> 
> I've sent this before, but as far as I can see, nothing's changed.
> 
> I'm having problems reading multiple large files at once. Reading 100 1GB
> files at once.
> 
> What happens is, when the buffer cache gets filled up, it all stalls, and
> transfer speed drops from 40-50 MB/s to a mere 2MB/s.

Re: [BUG] Error reading multiple large files

[Roy Sigurd Karlsbakk]

> Roy,
>
> I suspect this is a use-once effect.
>
> Could you please try http://surriel.com/patches/2.4/2.4.17-pre8-2ndchance
> ?

I tried it, but without any success. The vmstat output below indicate what
happens. As it shows, the 'bi' is quite stable (but slightly falling)
around 30-35 megs per sec. After the buffer memory is filled up/used, it
tries to swap out a little, works itself downwards before stabalizing at
~900kB/sec - from two 120G IDE drives in RAID-0 !!!

thanks for any help.

roy

   procs                      memory    swap          io     system         cpu
 r  b  w   swpd   free   buff  cache  si  so    bi    bo   in    cs  us  sy  id
 0 99  0      0 583376   7456 191076   0   0 34822     0  669   391   0   6  94
 0 99  0      0 513392   7540 258720   0   0 33864     0  657   458   0   9  91
 0 99  0      0 447432   7608 322484   0   0 31916     0  639   417   0   6  93
 0 99  0      0 379816   7692 387836   0   0 32718     0  666   354   1   7  92
 0 99  0      0 308704   7784 456560   0   0 34408     0  673   410   0   7  93
 0 99  0      0 237428   7876 525444   0   0 34486     0  670   407   1   7  92
 0 99  0      0 171460   7988 589172   0   0 31920     0  630   387   0   6  93
 0 99  0      0 110328   8080 648240   0   0 29582     0  634   295   1   4  95
 0 99  0      0  41876   8172 714392   0   0 33118     0 1076   552   0  13  87
 0 99  1    376   2340   1612 760852   0   0 33836     6  661   313   0  14  86
 0 99  1    376   3312   1288 760240   0   0 29870     0 1018   595   1  11  88
 0 99  2    376   3252   1260 760428   0   0 30616    22  667   447   1  11  88
 0 99  0    376   3268   1296 760344   0   0 25324     0  647   414   0   8  91
 0 99  1    376   3316   1320 760140   0   0 28272     0  700   500   0   6  93
 0 99  0    376   2564   1352 760920   0   0 25960     0  758   455   1   7  91
 0 99  0    376   3276   1372 760236   0   0 19910     0  746   415   0   6  93
 0 99  0    376   3264   1404 760108   0   0 18396     0  824   454   1   7  92
 0 99  0    376   3272   1444 760056   0   0 16324     0  846   480   0   6  94
 0 99  0    376   3268   1472 760024   0   0 14414     0  886   493   0   6  94
 0 99  0    376   3304   1500 759964   0   0 10630     0  891   463   0   6  94
 0 99  0    376   3244   1532 759984   0   0  7198     0  913   449   0   6  94
 0 99  0    376   3276   1564 759924   0   0  4730     0  920   488   0   4  96
 0 99  0    376   3264   1568 759924   0   0  4102     0  966   479   0   6  94
 0 99  0    376   3332   1584 759872   0   0   942     0  936   486   0   4  96
 0 99  0    376   3288   1584 759884   0   0   902     0  948   464   1   4  94
 0 99  0    376   3268   1584 759904   0   0   970     0  956   499   0   3  97


--
Roy Sigurd Karlsbakk, MCSE, MCNE, CLS, LCA

Computers are like air conditioners.
They stop working when you open Windows.

Re: [BUG] Error reading multiple large files

[Andrea Arcangeli]

On Mon, Jan 07, 2002 at 07:45:57PM +0100, Roy Sigurd Karlsbakk wrote:
> Hi all
> 
> I've sent this before, but as far as I can see, nothing's changed.
> 
> I'm having problems reading multiple large files at once. Reading 100 1GB
> files at once.
> 
> What happens is, when the buffer cache gets filled up, it all stalls, and
> transfer speed drops from 40-50 MB/s to a mere 2MB/s.
> 
> This has been tested on all versions from 2.4.16-2.4.18-pre1.

please try to reproduce on 2.4.18pre2aa2:

	ftp://ftp.us.kernel.org/pub/linux/kernel/people/andrea/kernels/v2.4/2.4.18pre2aa2.bz2

> 
> I've been testing Tux, Khttpd, apache 1.3.22, Apache 2, thttpd, cp and
> dd to verify the bug.

tux latest version is just included in -aa. please don't apply any
incremental patch before testing 18pre2aa2 to be sure the problem is not
introduced by some other patch.

> 
> Please help!
> 
> roy
> 
> --
> Roy Sigurd Karlsbakk, MCSE, MCNE, CLS, LCA
> 
> Computers are like air conditioners.
> They stop working when you open Windows.
> 
> -
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Andrea