Re: Lockless page cache test results

[Andrew Morton]

Jens Axboe <axboe@xxxxxxx> wrote:
>
> With a 16-page gang lookup in splice, the top profile for the 4-client
> case (which is now at 4GiB/sec instead of 3) are:
> 
> samples  %        symbol name
> 30396    36.7217  __do_page_cache_readahead
> 25843    31.2212  find_get_pages_contig
> 9699     11.7174  default_idle

__do_page_cache_readahead() should use gang lookup.  We never got around to
that, mainly because nothing really demonstrated a need.

It's a problem that __do_page_cache_readahead() is being called at all -
with everything in pagecache we should be auto-turning-off readahead.  This
happens because splice is calling the low-level do_pagecache_readahead(). 
If you convert it to use page_cache_readahead(), that will all vanish if
readahead is working right.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/