lkml.org 
[lkml]   [2018]   [Nov]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v2] mm: prototype: rid swapoff of quadratic complexity
From
Date
Hi Mathew,


Thanks for your response!

On 11/26/18 12:22 PM, Matthew Wilcox wrote:
> On Mon, Nov 26, 2018 at 04:55:21PM +0000, Vineeth Remanan Pillai wrote:
>> + do {
>> + XA_STATE(xas, &mapping->i_pages, start);
>> + int i;
>> + int entries = 0;
>> + struct page *page;
>> + pgoff_t indices[PAGEVEC_SIZE];
>> + unsigned long end = start + PAGEVEC_SIZE;
>>
>> + rcu_read_lock();
>> + xas_for_each(&xas, page, end) {
> I think this is a mistake. You should probably specify ULONG_MAX for the
> end. Otherwise if there are no swap entries in the first 60kB of the file,
> you'll just exit. That does mean you'll need to check 'entries' for
> hitting PAGEVEC_SIZE.

Thanks for pointing this out. I shall fix this in the next version.

> This seems terribly complicated. You run through i_pages, record the
> indices of the swap entries, then go back and look them up again by
> calling shmem_getpage() which calls the incredibly complex 300 line
> shmem_getpage_gfp().
>
> Can we refactor shmem_getpage_gfp() to skip some of the checks which
> aren't necessary when called from this path, and turn this into a nice
> simple xas_for_each() loop which works one entry at a time?

I shall investigate this and make this simpler as you suggested.

>> + list_for_each_safe(p, next, &shmem_swaplist) {
>> + info = list_entry(p, struct shmem_inode_info, swaplist);
> This could use list_for_each_entry_safe(), right?

Yes, you are right. Will fix.


Thanks,

Vineeth

>

\
 
 \ /
  Last update: 2018-11-26 19:36    [W:0.074 / U:0.616 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site