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From Weijun Li <weiju...@gmail.com>
Subject Re: Testing row cache feature in trunk: write should put record in cache
Date Wed, 17 Feb 2010 19:51:33 GMT
OK I'll work on the change later because there's another problem to solve:
the overhead for cache is too big that 1.4mil records (1k each) consumed all
of the 6gb memory of JVM (I guess 4gb are consumed by the row cache). I'm
thinking that ConcurrentHashMap is not a good choice for LRU and the row
cache needs to store compressed key data to reduce memory usage. I'll do
more investigation on this and let you know.

-Weijun

On Tue, Feb 16, 2010 at 9:22 PM, Jonathan Ellis <jbellis@gmail.com> wrote:

> ... tell you what, if you write the option-processing part in
> DatabaseDescriptor I will do the actual cache part. :)
>
> On Tue, Feb 16, 2010 at 11:07 PM, Jonathan Ellis <jbellis@gmail.com>
> wrote:
> > https://issues.apache.org/jira/secure/CreateIssue!default.jspa<https://issues.apache.org/jira/secure/CreateIssue%21default.jspa>,
> but
> > this is pretty low priority for me.
> >
> > On Tue, Feb 16, 2010 at 8:37 PM, Weijun Li <weijunli@gmail.com> wrote:
> >> Just tried to make quick change to enable it but it didn't work out :-(
> >>
> >>                ColumnFamily cachedRow =
> cfs.getRawCachedRow(mutation.key());
> >>
> >>                 // What I modified
> >>                 if( cachedRow == null ) {
> >>                     cfs.cacheRow(mutation.key());
> >>                     cachedRow = cfs.getRawCachedRow(mutation.key());
> >>                 }
> >>
> >>                 if (cachedRow != null)
> >>                     cachedRow.addAll(columnFamily);
> >>
> >> How can I open a ticket for you to make the change (enable row cache
> write
> >> through with an option)?
> >>
> >> Thanks,
> >> -Weijun
> >>
> >> On Tue, Feb 16, 2010 at 5:20 PM, Jonathan Ellis <jbellis@gmail.com>
> wrote:
> >>>
> >>> On Tue, Feb 16, 2010 at 7:17 PM, Jonathan Ellis <jbellis@gmail.com>
> wrote:
> >>> > On Tue, Feb 16, 2010 at 7:11 PM, Weijun Li <weijunli@gmail.com>
> wrote:
> >>> >> Just started to play with the row cache feature in trunk: it seems
> to
> >>> >> be
> >>> >> working fine so far except that for RowsCached parameter you need
to
> >>> >> specify
> >>> >> number of rows rather than a percentage (e.g., "20%" doesn't work).
> >>> >
> >>> > 20% works, but it's 20% of the rows at server startup.  So on a fresh
> >>> > start that is zero.
> >>> >
> >>> > Maybe we should just get rid of the % feature...
> >>>
> >>> (Actually, it shouldn't be hard to update this on flush, if you want
> >>> to open a ticket.)
> >>
> >>
> >
>

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