From: Chuck Lever <cel@citi.umich.edu>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Junio C Hamano <junkio@cox.net>, git@vger.kernel.org
Subject: Re: [PATCH 0/2] A new merge algorithm, take 3
Date: Thu, 08 Sep 2005 14:16:06 -0400 [thread overview]
Message-ID: <43207FE6.2030108@citi.umich.edu> (raw)
In-Reply-To: <Pine.LNX.4.58.0509081012540.3208@g5.osdl.org>
[-- Attachment #1: Type: text/plain, Size: 1599 bytes --]
Linus Torvalds wrote:
>
> On Thu, 8 Sep 2005, Junio C Hamano wrote:
>
>>Yes, the reading of three trees upfront is probably the culprit
>>in your case
>
>
> However, note that _most_ tree reading just reads one.
>
> Merges may take half a second, and yes, when I did it, the fact that we
> move things around in the array is by far the highest cost. But the thing
> is, if merges take half a second, that's still not only damn good, it's
> not even the most common operation.
in my case the merges were taking significantly longer than a half
second. making this change is certainly not worth it if merges are
running fast...
> Yes, the active_cache[] layout as one big array is inconvenient for
> read_tree(), which tends to want to interleave different trees in the
> array and thus forces things to be moved around.
>
> But remember what the most common use for the index is - it's the "single
> tree" case from read_cache(). That's _so_ much more common than
> read_tree() that it's not even funny.
read_cache is fast as implemented. the issue is that the next thing
that is often done is a cache insert, which requires a memmove, which is
slow.
> So the data structure is optimized for a different case than reading in
> trees. Big deal. That optimization is definitely worth it: it allows us to
> do the read_cache() with the actual index entries being totally read-only
> (a linked list would have to add a "next" pointer to the cache entries and
> not allow the in-place thing that read_cache() does).
they are still read-only with my linked list implementation.
[-- Attachment #2: cel.vcf --]
[-- Type: text/x-vcard, Size: 439 bytes --]
begin:vcard
fn:Chuck Lever
n:Lever;Charles
org:Network Appliance, Incorporated;Linux NFS Client Development
adr:535 West William Street, Suite 3100;;Center for Information Technology Integration;Ann Arbor;MI;48103-4943;USA
email;internet:cel@citi.umich.edu
title:Member of Technical Staff
tel;work:+1 734 763-4415
tel;fax:+1 734 763 4434
tel;home:+1 734 668-1089
x-mozilla-html:FALSE
url:http://www.monkey.org/~cel/
version:2.1
end:vcard
next prev parent reply other threads:[~2005-09-08 18:16 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-07 16:47 [PATCH 0/2] A new merge algorithm, take 3 Fredrik Kuivinen
2005-09-07 16:50 ` [PATCH 1/2] Add '-i' flag to read-tree to make it ignore whats in the working directory Fredrik Kuivinen
2005-09-11 2:54 ` Unified merge driver pushed out to "master" branch Junio C Hamano
2005-09-11 21:05 ` Fredrik Kuivinen
2005-09-12 1:23 ` Junio C Hamano
2005-09-14 5:56 ` Another merge test case from the kernel tree Junio C Hamano
2005-09-14 16:11 ` Daniel Barkalow
2005-09-14 16:30 ` Junio C Hamano
2005-09-14 17:42 ` Fredrik Kuivinen
2005-09-14 17:51 ` Junio C Hamano
2005-09-15 0:47 ` Yet another set of merge test cases " Junio C Hamano
2005-09-19 16:13 ` Fredrik Kuivinen
2005-09-20 1:53 ` Junio C Hamano
2005-09-20 5:50 ` Fredrik Kuivinen
2005-09-07 16:51 ` [PATCH 2/2] A new merge algorithm Fredrik Kuivinen
2005-09-07 18:33 ` [PATCH 0/2] A new merge algorithm, take 3 Daniel Barkalow
2005-09-08 6:06 ` Fredrik Kuivinen
2005-09-08 15:27 ` Daniel Barkalow
2005-09-08 20:05 ` Fredrik Kuivinen
2005-09-08 21:27 ` Daniel Barkalow
2005-09-07 18:36 ` Junio C Hamano
[not found] ` <431F34FF.5050301@citi.umich.edu>
[not found] ` <7vvf1cz64l.fsf@assigned-by-dhcp.cox.net>
2005-09-08 15:06 ` Chuck Lever
2005-09-08 16:51 ` Junio C Hamano
2005-09-08 17:19 ` Linus Torvalds
2005-09-08 17:51 ` Junio C Hamano
2005-09-08 18:16 ` Chuck Lever [this message]
2005-09-08 18:35 ` Linus Torvalds
2005-09-08 18:58 ` Chuck Lever
2005-09-08 20:59 ` Linus Torvalds
2005-09-09 7:44 ` [RFH] Merge driver Junio C Hamano
2005-09-09 16:05 ` Daniel Barkalow
2005-09-09 16:43 ` Junio C Hamano
2005-09-09 17:25 ` Daniel Barkalow
2005-09-11 4:58 ` Junio C Hamano
2005-09-12 21:08 ` Fredrik Kuivinen
2005-09-12 21:16 ` Junio C Hamano
2005-09-13 20:33 ` Fredrik Kuivinen
2005-09-13 20:46 ` Junio C Hamano
2005-09-08 20:54 ` [PATCH 0/2] A new merge algorithm, take 3 Junio C Hamano
2005-09-08 21:23 ` A Large Angry SCM
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=43207FE6.2030108@citi.umich.edu \
--to=cel@citi.umich.edu \
--cc=git@vger.kernel.org \
--cc=junkio@cox.net \
--cc=torvalds@osdl.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).