Re: 2.6.12-rc6-mm1 & 2K lun testing

From: Andrew Morton
Date: Thu Jun 16 2005 - 02:27:13 EST

Badari Pulavarty <pbadari@xxxxxxxxxx> wrote:
> I sniff tested 2K lun support with 2.6.12-rc6-mm1 on
> my AMD64 box. I had to tweak qlogic driver and
> scsi_scan.c to see all the luns.
> (2.6.12-rc6 doesn't see all the LUNS due to max_lun
> issue - which is fixed in scsi-git tree).
> Test 1:
> run dds on all 2048 "raw" devices - worked
> great. No issues.
> Tests 2:
> run "dds" on 2048 filesystems (one file
> per filesystem). Kind of works. I was expecting better
> responsiveness & stability.
> Overall - Good news is, it works.
> Not so good news - with filesystem tests, machine becomes
> unresponsive, lots of page allocation failures but machine
> stays up and completes the tests and recovers.

Any chance of getting a peek at /proc/slabinfo?

Presumably increasing /proc/sys/vm/min_free_kbytes will help.

We seem to be always ooming when allocating scsi command structures.
Perhaps the block-level request structures are being allocated with
__GFP_WAIT, but it's a bit odd. Which I/O scheduler? If cfq, does
reducing /sys/block/*/queue/nr_requests help?

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