From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Curt Sampson <cjs(at)cynic(dot)net> |
Cc: | Kevin Brown <kevin(at)sysexperts(dot)com>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: First set of OSDL Shared Mem scalability results, some wierdness ... |
Date: | 2004-10-23 18:11:04 |
Message-ID: | 26467.1098555064@sss.pgh.pa.us |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers pgsql-performance |
Curt Sampson <cjs(at)cynic(dot)net> writes:
> Back when I was working out how to do this, I reckoned that you could
> use mmap by keeping a write queue for each modified page. Reading,
> you'd have to read the datum from the page and then check the write
> queue for that page to see if that datum had been updated, using the
> new value if it's there. Writing, you'd add the modified datum to the
> write queue, but not apply the write queue to the page until you'd had
> confirmation that the corresponding transaction log entry had been
> written. So multiple writes are no big deal; they just all queue up in
> the write queue, and at any time you can apply as much of the write
> queue to the page itself as the current log entry will allow.
Seems to me the overhead of any such scheme would swamp the savings from
avoiding kernel/userspace copies ... the locking issues alone would be
painful.
regards, tom lane
From | Date | Subject | |
---|---|---|---|
Next Message | Steve Crawford | 2004-10-23 21:16:34 | Re: Time off |
Previous Message | Oliver Elphick | 2004-10-23 15:59:26 | Re: Slony-I 1.0.4 Released |
From | Date | Subject | |
---|---|---|---|
Next Message | Tom Lane | 2004-10-23 18:21:10 | Re: futex results with dbt-3 |
Previous Message | Bjorn Bength | 2004-10-23 15:54:05 | different io elevators in linux |