Re: [Bugme-new] [Bug 31142] New: Large write to USB stick freezes unrelated tasks for a long time

["Alex Villací­s Lasso" <avillaci@fiec.espol.edu.ec>]

El 12/04/11 11:27, Alex Villaci-s Lasso escribio:
>>> ===
>>> Subject: compaction: reverse the change that forbid sync migraton with __GFP_NO_KSWAPD
>>>
>>> From: Andrea Arcangeli<aarcange@redhat.com>
>>>
>>> It's uncertain this has been beneficial, so it's safer to undo it. All other
>>> compaction users would still go in synchronous mode if a first attempt of async
>>> compaction failed. Hopefully we don't need to force special behavior for THP
>>> (which is the only __GFP_NO_KSWAPD user so far and it's the easier to exercise
>>> and to be noticeable). This also make __GFP_NO_KSWAPD return to its original
>>> strict semantics specific to bypass kswapd, as THP allocations have khugepaged
>>> for the async THP allocations/compactions.
>>>
>>> Signed-off-by: Andrea Arcangeli<aarcange@redhat.com>
>>> ---
>>>   mm/page_alloc.c |    2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> --- a/mm/page_alloc.c
>>> +++ b/mm/page_alloc.c
>>> @@ -2105,7 +2105,7 @@ rebalance:
>>>                       sync_migration);
>>>       if (page)
>>>           goto got_pg;
>>> -    sync_migration = !(gfp_mask&  __GFP_NO_KSWAPD);
>>> +    sync_migration = true;
>>>
>>>       /* Try direct reclaim and then allocating */
>>>       page = __alloc_pages_direct_reclaim(gfp_mask, order,
>>>
>> The stalls occur even with vfat. I am no longer using udf, since (right now) it is not necessary. I will test this patch now.
>>
>
> From preliminary tests, I feel that the patch actually eliminates the stalls. I have just copied nearly 6 GB of data into my USB stick and noticed no application freezes.
>
I retract that. I have tested 2.6.39-rc3 after a day of having several heavy applications loaded in memory, and the stalls do get worse when reversing the patch.

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