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Re: [Proposal] Remove DAV properties cache in ra_serf

From: Hyrum K Wright <hyrum_at_hyrumwright.org>
Date: Tue, 15 Feb 2011 10:44:02 +0000

On Tue, Feb 15, 2011 at 6:42 AM, Greg Stein <gstein_at_gmail.com> wrote:
> On Mon, Feb 14, 2011 at 14:14, C. Michael Pilato <cmpilato_at_collab.net> wrote:
>> On 02/14/2011 01:57 PM, Ivan Zhakov wrote:
>>> Hi,
>>>
>>> Currently ra_serf caches *all* DAV properties retrieved using PROPFIND
>>> in session pool. This was attempt to reduce number of PROPFIND
>>> requests. But current implementation has several problems:
>>> 1. Unlimited memory usage: current implementation stores all
>>> properties, so svn ls -R command can easily eat 150 mb of memory.
>>> 2. Very low cache hit due the fact that cache doesn't support caching
>>> "allprop" requests. For some operations there is no hits at all.
>>> 3. Current implementation caches properties that may change between
>>> requests, like URL to youngest revision.
>>>
>>> Of course these problems can be fixed, but I'm not sure that we need
>>> this code. Since in svn 1.7 we have HTTPv2 which doesn't use so many
>>> PROPFIND requests that we tried to reduce using DAV properties cache.
>>>
>>> So I'm propose just to remove DAV properties cache from ra_serf.
>>> Objections? Comments?
>>>
>>> PS: See attached patch in case you'd like test performance.
>>
>> Ivan,
>>
>> Thanks so much for looking so closely into ra_serf recently!  It hadn't
>> occurred to me when implementing the HTTPv2 stuff that the prop cache might
>> become less useful as a result.
>>
>> But what is the effect for older servers?  Would it make sense keep the
>> cache logic, but conditionally use it only for non-HTTPv2 connections?
>
> Note that removing the cache will not *break* the code. It simply
> makes operation a bit slower.
>
> "upgrade your server"
>
> Given that we can simplify the client (remove caching), and given that
> we can avoid unbounded memory usage, and that we don't really need the
> cache... it seems like a win.

How far can we go with this? If we're not using cached DAV properties
with ra_serf, and ra_serf is the default in 1.7, does it make sense to
remove support for them from the 1.7 working copy? It shouldn't be
too difficult, and would tighten libsvn_wc up a bit.

-Hyrum
Received on 2011-02-15 11:44:42 CET

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