Messages in this thread | | | From | Daniel Phillips <> | Subject | Re: [patch] truncate_inode_pages | Date | Sun, 10 Jun 2001 00:53:36 +0200 |
| |
On Saturday 09 June 2001 19:40, Alexander Viro wrote: > > takes 45 seconds CPU time due to the O(clean * dirty) algorithm in > > truncate_inode_pages(). The machine is locked up for the duration. > > The patch reduces this to 20 milliseconds via an O(clean + dirty) > > algorithm. > > Unfortunately, it's _not_ O(clean + dirty). > > > + while (truncate_list_pages(&mapping->clean_pages, start, > > &partial)) { + spin_lock(&pagecache_lock); > > + complete = 0; > > + } > > Cool. Now think what happens if pages with large indices are in the > very end of list. Half of them. You skip clean/2 pages on each of > clean/2 passes. Hardly a linear behaviour - all you need is a > different program to trigger it. > > Now, having a separate pass that would reorder the pages on list, > moving the to-kill ones in the beginning might help.
This is easy, just set the list head to the page about to be truncated.
-- Daniel - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |