Hi,
On 10/29/2015 09:30 AM, Sage Weil wrote:
On Thu, 29 Oct 2015, Yan, Zheng wrote:
On Thu, Oct 29, 2015 at 2:21 PM, Gregory Farnum <gfarnum@xxxxxxxxxx> wrote:
On Wed, Oct 28, 2015 at 8:38 PM, Yan, Zheng <ukernel@xxxxxxxxx> wrote:
On Thu, Oct 29, 2015 at 1:10 AM, Burkhard Linke
I tried to dig into the ceph-fuse code, but I was unable to find the
fragment that is responsible for flushing the data from the page cache.
fuse kernel code invalidates page cache on opening file. you can
disable this behaviour by setting ""fuse use invalidate cb" config
option to true.
With that option ceph-fuse finally works with page cache:
$ time cat /ceph/volumes/biodb/asn1/nr.3*.psq > /dev/null
real 2m0.979s
user 0m0.020s
sys 0m3.164s
$ time cat /ceph/volumes/biodb/asn1/nr.3*.psq > /dev/null
real 0m2.106s
user 0m0.000s
sys 0m1.996s
Zheng, do you know any reason we shouldn't make that the default value
now? There was a loopback deadlock (which is why it's disabled by
default) but I don't remember the details offhand well enough to know
if your recent work in those interfaces has fixed it. Or Sage?
-Greg
there is no loopback deadlock now, because we use a separate thread to
invalidate kernel page cache. I think we can enable this option
safely.
...as long as nobody blocks waiting for invalidate while holding a lock
(client_lock?) that could prevent other fuse ops like write (pretty sure
that was the deadlock we saw before). I worry this could still happen
with a writer (or reader?) getting stuck in a check_caps() type situation
while the invalidate cb is waiting on a page lock held by the calling
kernel syscall...
I have created an issue to track this: http://tracker.ceph.com/issues/13640
It would be great it the patch is ported to one of the next hammer
releases after the potential deadlock situation is analysed.
Best regards,
Burkhard
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