Re: [PATCH] ext4: slab caches set to SLAB_MEM_SPREAD flags.

[NamJae Jeon]

2011/11/19 Theodore Tso <tytso@xxxxxxx>:
>
> On Nov 19, 2011, at 8:52 AM, NamJae Jeon wrote:
>
>> 2011/11/18 Theodore Tso <tytso@xxxxxxx>:
>>>
>>> On Nov 17, 2011, at 10:11 AM, Theodore Tso wrote:
>>>>
>>>> So accessing non-local memory can be a really, really big deal. ÂAnd this
>>>> isn't just theoretical, but have you considered what might happen on a 8
>>>> core AMD machine?
>>>
>>> Sorry, typo. ÂThis should have read, "have you considered what might happen on a 8 _socket_ AMD machine"?
>>>
>> You're right. but..
>> It is only useful using cpuset, And have you read cpuset spread
>> history link of Amit provided ?
>> And why have you still used spread flags for inode cache ?
>
> The inode cache is different for the following reasons:
>
> (1) The memory allocations are long-lived, and there is a good chance for many of them that they will be used by other CPU's on different NUMA nodes.
>
> (2) ÂThere are a very large number of inodes, so uneven allocation of the inodes has a significantly larger impact.
>
> In contrast, the page_io and mballoc allocations are very short lived, there aren't a whole lot of them (check /proc/slabinfo), and they are guaranteed to be used during their very short lifetime on the local CPU node. Â So the benefits of spreading them around are not that great, since they aren't that many of them, and downsides of potential 2x or 3x time to access memory is large.
>
Thanks for your opinion.
Have you thought that mem spread flags is not needed in group info
caches same with page_io and mballoc ?

> -- Ted
>
>
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