Messages in this thread | | | Date | Sun, 7 Sep 2014 22:48:51 +0200 | From | Volker Lendecke <> | Subject | Re: read()/readv() only from page cache |
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On Fri, Sep 05, 2014 at 12:27:21PM -0400, Milosz Tanski wrote: > In a VLDB like workload this would enable me to lower the latency of > common fast requests and. By fast requests I mean ones that do not > require much data, the data is cached, or there's a predictable read > pattern (read-ahead). Obviously it would be at the expense of the > latency of large/slow requests (they have to make 2 read calls, the > first one always EWOULDBLOCK) ... but in that case it doesn't matter > since the time to do actual IO would trump any kind of extra latency.
That was my thinking as well when I discussed it with Christoph. Sorry for not getting around to actually test his patch. Samba right now uses a thread pool for aio, we get parallel read requests from clients over a single TCP connection and we need to keep all disks busy simultaneously. We'd like to avoid the thread overhead when it's not necessary because the data is already around. A per-request flag would fit Samba better than a flag settable by fcntl in this pattern. Samba can't easily open a file twice (once with NONBLOCK and once without).
Volker
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