[Gluster-users] help me, glusterfs 3.3 doen't support fopen-keep-cache?

[Brian Foster]

On 01/09/2013 08:06 AM, 符永涛 wrote:
> Hi Brian,
> I check the review of c1fe8b7fd7 and find there's only one line code
> change. I change accordingly in glusterfs3.3 and find page cache works
> which boost performance for my usecase.

Well c1fe8b7fd7 is a bit more than a one line change, but it is a
relatively simple compatibility check just to ensure that your version
of fuse supports the ability to invalidate cache mapping on demand. I
didn't catch it when fopen-keep-cache first went in, so hence it was
added after the fact. Glad to hear that this works for you, though!

> 1 Besides make it a configurable mount option do I need to change any
> other code?

Nope, I think those two commits should be enough.

> 2 Is there any side effect for doing this(FOPEN_KEEP_CACHE)?

Just that open() operations will no longer unconditionally invalidate
page cache mappings for files. The gluster md-cache translator will now
become responsible for clearing the local cache. If it detects that the
remote inode has changed since the version it has last cached (size or
mtime, iirc), it will poke fuse to invalidate the local page cache. You
should be able to test this mechanism by doing a 'touch <file>' on one
of your bricks and verifying that the client now re-reads the file.

> 3 I noticed this can be achied with only client side code change. Can
> I only compile client side rpm and install it without any server side
> upgrade(If this is true the upgrade impact and risk is much lower for
> me since I'm running gluster in production)?
> 

Correct, this is a client side only change. You should be able to deploy
this on clients without modification to existing servers, provided
things work as they are.

Brian

> Thank you very much.
> 
> 2013/1/9, Brian Foster <bfoster at redhat.com>:
>> On 01/08/2013 06:42 PM, yongtaofu wrote:
>>> Hi brian
>>> Thank you very much for your info.
>>> I have already tried io-cache it helps a little but it can't compete with
>>> page cache.
>>> BTW what's the effort if I want to back port fopen keep cache to 3.3?
>>>
>>
>> No problem. I don't think it should be that difficult to pull back the
>> keep cache patch to 3.3 if you wanted to, but feel free to ping me if
>> you have trouble with it.
>>
>> Note that you probably want to include the following commit as well:
>>
>> c1fe8b7fd7 mount/fuse: check for fuse inval notify support when
>> fopen-keep-cache enabled
>>
>> Brian
>>
>>> 发自我的 iPhone
>>>
>>> 在 2013-1-8，23:21，Brian Foster <bfoster at redhat.com> 写道：
>>>
>>>> On 01/08/2013 09:49 AM, 符永涛 wrote:
>>>>> Dear gluster experts,
>>>>>
>>>>> I search through glusterfs 3.3 source tree and can't find any fuse
>>>>> open option FOPEN_KEEP_CACHE related code. Does this mean that
>>>>> glusterfs 3.3 doen't support fuse keep cache feature? However I did
>>>>> find keep cache code in mainline. My question is:
>>>>
>>>> It appears that keep cache support is not included in the 3.3 release.
>>>> You can build from the latest git repo to try it:
>>>>
>>>> 32ffb79f fuse/md-cache: add support for the 'fopen-keep-cache' mount
>>>> option
>>>>
>>>>> 1 does glusterfs 3.3 support page cache?
>>>>
>>>> Page cache interaction is primarily a function of fuse. The current
>>>> behavior is that writes are synchronous to the fuse filesystem, reads
>>>> are potentially served from page cache, and file open operations
>>>> invalidate the entire mapping for a file.
>>>>
>>>> The FOPEN_KEEP_CACHE fuse init option disables the latter behavior. In
>>>> turn, gluster detects whether changes have occurred in the file remotely
>>>> and nudges fuse to invalidate the file cache on-demand. There is also
>>>> upstream fuse work in progress to support writeback cache behavior[1].
>>>>
>>>>> 2 if not what is the best practice to improve performance if a file is
>>>>> frequently accessed by read especially through random access fops.
>>>>
>>>> I would suggest to experiment with the tunables in the io-cache
>>>> translator (xlators/performance/io-cache/src/io-cache.c), such as
>>>> priority, cache-timeout and cache-size.
>>>>
>>>>> 3 does glusterfs 3.4 support page cache, if supported how to enable it
>>>>> through mount option?
>>>>
>>>> I would hope that it will at least include the keep cache support. Use
>>>> the fopen-keep-cache mount option on latest gluster to try it out.
>>>>
>>>> Brian
>>>>
>>>> [1] - http://comments.gmane.org/gmane.comp.file-systems.fuse.devel/12266
>>>>
>>>>> Thank you very much.
>>>>
>>
>>
> 
>