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From: Jeff King <peff@peff.net>
To: Derrick Stolee <stolee@gmail.com>
Cc: git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH v2 02/15] pack-bitmap: fix leak of haves/wants object lists
Date: Tue, 18 Feb 2020 15:02:19 -0500
Message-ID: <20200218200219.GC21774@coredump.intra.peff.net> (raw)
In-Reply-To: <28c2f199-e9eb-4405-9044-92a0af7632ec@gmail.com>

On Tue, Feb 18, 2020 at 12:58:10PM -0500, Derrick Stolee wrote:

> On 2/14/2020 1:22 PM, Jeff King wrote:
> > When we do a bitmap-aware revision traversal, we create an object_list
> > for each of the "haves" and "wants" tips. After creating the result
> > bitmaps these are no longer needed or used, but we never free the list
> > memory.
> 
> It's surprising that we got away with this for so long. Is it
> possible that this loop of freeing memory could provide significant
> performance drawbacks? I'm assuming that the free() loop is much
> faster than the malloc() loop, so the impact is negligible.

I don't think it's surprising. We're only talking about leaking hundreds
or perhaps thousands of structs. So maybe a few kilobytes at most. And
we'd typically only run one such bitmap traversal per program.

Meanwhile rev-list is generally storing that same set of objects in a
pending array, and I think we don't generally clean up after it (nor is
there even a convenient function to do so).

So I think it's sort of a drop in the bucket of Git's "eh, this pretty
much lasts about the whole program anyway" leaks. I don't think there's
much performance difference either way in freeing or not. It's mostly
just a cleanliness thing. (I do one day dream of being able to run the
test suite through a leakchecker, but we're still a ways off, I think).

-Peff

  reply index

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-13  2:15 [PATCH 0/13] combining object filters and bitmaps Jeff King
2020-02-13  2:16 ` [PATCH 01/13] pack-bitmap: factor out type iterator initialization Jeff King
2020-02-13 17:45   ` Junio C Hamano
2020-02-13  2:16 ` [PATCH 02/13] pack-bitmap: fix leak of haves/wants object lists Jeff King
2020-02-13 18:12   ` Junio C Hamano
2020-02-13  2:17 ` [PATCH 03/13] rev-list: fallback to non-bitmap traversal when filtering Jeff King
2020-02-13 18:19   ` Junio C Hamano
2020-02-13 18:40     ` Jeff King
2020-02-13  2:17 ` [PATCH 04/13] rev-list: consolidate bitmap-disabling options Jeff King
2020-02-13  2:18 ` [PATCH 05/13] rev-list: factor out bitmap-optimized routines Jeff King
2020-02-13 18:34   ` Junio C Hamano
2020-02-13  2:19 ` [PATCH 06/13] rev-list: make --count work with --objects Jeff King
2020-02-13 19:14   ` Junio C Hamano
2020-02-13 20:27     ` Jeff King
2020-02-13  2:20 ` [PATCH 07/13] rev-list: allow bitmaps when counting objects Jeff King
2020-02-13 21:47   ` Junio C Hamano
2020-02-13 22:27     ` Jeff King
2020-02-13  2:20 ` [PATCH 08/13] pack-bitmap: basic noop bitmap filter infrastructure Jeff King
2020-02-13  2:21 ` [PATCH 09/13] rev-list: use bitmap filters for traversal Jeff King
2020-02-13 22:22   ` Junio C Hamano
2020-02-13 22:34     ` Jeff King
2020-02-13  2:21 ` [PATCH 10/13] bitmap: add bitmap_unset() function Jeff King
2020-02-13  2:23 ` [PATCH 11/13] pack-bitmap: implement BLOB_NONE filtering Jeff King
2020-02-13  2:25 ` [PATCH 12/13] pack-bitmap: implement BLOB_LIMIT filtering Jeff King
2020-02-13 23:17   ` Junio C Hamano
2020-02-13  2:25 ` [PATCH 13/13] pack-objects: support filters with bitmaps Jeff King
2020-02-14 18:21 ` [PATCH v2 0/15] combining object filters and bitmaps Jeff King
2020-02-14 18:22   ` [PATCH v2 01/15] pack-bitmap: factor out type iterator initialization Jeff King
2020-02-15  0:10     ` Taylor Blau
2020-02-14 18:22   ` [PATCH v2 02/15] pack-bitmap: fix leak of haves/wants object lists Jeff King
2020-02-15  0:15     ` Taylor Blau
2020-02-15  6:46       ` Jeff King
2020-02-18 17:58     ` Derrick Stolee
2020-02-18 20:02       ` Jeff King [this message]
2020-02-14 18:22   ` [PATCH v2 03/15] rev-list: fallback to non-bitmap traversal when filtering Jeff King
2020-02-15  0:22     ` Taylor Blau
2020-02-14 18:22   ` [PATCH v2 04/15] pack-bitmap: refuse to do a bitmap traversal with pathspecs Jeff King
2020-02-14 19:03     ` Junio C Hamano
2020-02-14 20:51       ` Jeff King
2020-02-14 18:22   ` [PATCH v2 05/15] rev-list: factor out bitmap-optimized routines Jeff King
2020-02-15  0:35     ` Taylor Blau
2020-02-14 18:22   ` [PATCH v2 06/15] rev-list: make --count work with --objects Jeff King
2020-02-15  0:42     ` Taylor Blau
2020-02-15  6:48       ` Jeff King
2020-02-16 23:34         ` Junio C Hamano
2020-02-18  5:24           ` Jeff King
2020-02-18 17:28             ` Junio C Hamano
2020-02-18 19:55               ` Jeff King
2020-02-18 21:19                 ` Junio C Hamano
2020-02-18 21:23                   ` Jeff King
2020-02-18 18:05     ` Derrick Stolee
2020-02-18 19:59       ` Jeff King
2020-02-14 18:22   ` [PATCH v2 07/15] rev-list: allow bitmaps when counting objects Jeff King
2020-02-15  0:45     ` Taylor Blau
2020-02-15  6:55       ` Jeff King
2020-02-16 23:36         ` Junio C Hamano
2020-02-14 18:22   ` [PATCH v2 08/15] t5310: factor out bitmap traversal comparison Jeff King
2020-02-15  2:14     ` Taylor Blau
2020-02-15  7:00       ` Jeff King
2020-02-14 18:22   ` [PATCH v2 09/15] rev-list: allow commit-only bitmap traversals Jeff King
2020-02-18 18:18     ` Derrick Stolee
2020-02-18 20:05       ` Jeff King
2020-02-18 20:11         ` Derrick Stolee
2020-02-14 18:22   ` [PATCH v2 10/15] pack-bitmap: basic noop bitmap filter infrastructure Jeff King
2020-02-14 18:22   ` [PATCH v2 11/15] rev-list: use bitmap filters for traversal Jeff King
2020-02-14 18:22   ` [PATCH v2 12/15] bitmap: add bitmap_unset() function Jeff King
2020-02-14 18:22   ` [PATCH v2 13/15] pack-bitmap: implement BLOB_NONE filtering Jeff King
2020-02-18 19:26     ` Derrick Stolee
2020-02-18 19:36       ` Derrick Stolee
2020-02-18 20:30         ` Jeff King
2020-02-18 20:24       ` Jeff King
2020-02-14 18:22   ` [PATCH v2 14/15] pack-bitmap: implement BLOB_LIMIT filtering Jeff King
2020-02-14 18:22   ` [PATCH v2 15/15] pack-objects: support filters with bitmaps Jeff King

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