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From: Jeff King <peff@peff.net>
To: Duy Nguyen <pclouds@gmail.com>
Cc: Elijah Newren <newren@gmail.com>, Git Mailing List <git@vger.kernel.org>
Subject: Re: 2.18.0 Regression: packing performance and effectiveness
Date: Thu, 19 Jul 2018 13:04:00 -0400	[thread overview]
Message-ID: <20180719170400.GC4868@sigill.intra.peff.net> (raw)
In-Reply-To: <20180719151640.GA24997@duynguyen.home>

On Thu, Jul 19, 2018 at 05:16:42PM +0200, Duy Nguyen wrote:

> On Thu, Jul 19, 2018 at 07:57:37AM +0200, Duy Nguyen wrote:
> > I thought 2M was generous but I was obviously wrong. I'd like to see
> > the biggest delta size in this pack and whether it's still reasonable
> > to increase OE_DELTA_SIZE_BITS. But if it's very close to 4GB limit
> > then we could just store 64-bit delta size in a separate array.
> 
> I realize now that these two options don't have to be mutually
> exclusive and I should provide a good fallback in terms of performance
> anyway.

Yeah, this is what I had assumed was happening in the original code. :)

> +void oe_prepare_delta_size_array(struct packing_data *pack)
> +{
> +	int i;
> +
> +	/*
> +	 * nr_alloc, not nr_objects to align with realloc() strategy in
> +	 * packlist_alloc()
> +	 */
> +	ALLOC_ARRAY(pack->delta_size, pack->nr_alloc);
> +
> +	for (i = 0; i < pack->nr_objects; i++)
> +		pack->delta_size[i] = pack->objects[i].delta_size_;
> +}

This iterator should probably be a uint32_t, to match nr_objects.

The rest of the patch looks OK to me. From Elijah's failure report there
clearly is _some_ problem where we end up with a truncated write of a
delta. But I don't see it from code inspection, nor could I reproduce
it.

-Peff

  parent reply	other threads:[~2018-07-19 17:04 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-18 22:51 2.18.0 Regression: packing performance and effectiveness Elijah Newren
2018-07-18 22:51 ` [RFC PATCH] fix-v1: revert "pack-objects: shrink delta_size field in struct object_entry" Elijah Newren
2018-07-18 22:51 ` [RFC PATCH] fix-v2: make OE_DELTA_SIZE_BITS a bit bigger Elijah Newren
2018-07-19  5:41 ` 2.18.0 Regression: packing performance and effectiveness Duy Nguyen
2018-07-19  5:49   ` Jeff King
2018-07-19 15:27   ` Elijah Newren
2018-07-19 15:43     ` Duy Nguyen
2018-07-19  5:44 ` Jeff King
2018-07-19  5:57   ` Duy Nguyen
2018-07-19 15:16     ` Duy Nguyen
2018-07-19 16:42       ` Elijah Newren
2018-07-19 17:23         ` Jeff King
2018-07-19 17:31           ` Duy Nguyen
2018-07-19 18:24             ` Duy Nguyen
2018-07-19 19:17               ` Jeff King
2018-07-19 23:11               ` Elijah Newren
2018-07-20  5:28                 ` Jeff King
2018-07-20  5:30                   ` Jeff King
2018-07-20  5:47                   ` Duy Nguyen
2018-07-20 17:21                   ` Elijah Newren
2018-07-19 17:04       ` Jeff King [this message]
2018-07-19 19:25       ` Junio C Hamano
2018-07-19 19:27         ` Junio C Hamano
2018-07-20 15:39 ` [PATCH] pack-objects: fix performance issues on packing large deltas Nguyễn Thái Ngọc Duy
2018-07-20 17:40   ` Jeff King
2018-07-21  4:23     ` Duy Nguyen
2018-07-23 21:37       ` Jeff King
2018-07-20 17:43   ` Elijah Newren
2018-07-20 23:52     ` Elijah Newren
2018-07-21  4:07       ` Duy Nguyen
2018-07-21  7:08         ` Duy Nguyen
2018-07-21  4:47     ` Duy Nguyen
2018-07-21  6:56       ` Elijah Newren
2018-07-21  7:14         ` Duy Nguyen
2018-07-22  6:22       ` Elijah Newren
2018-07-22  6:49         ` Duy Nguyen
2018-07-23 12:34     ` Elijah Newren
2018-07-23 15:50       ` Duy Nguyen
2018-07-22  8:04   ` [PATCH v2] " Nguyễn Thái Ngọc Duy
2018-07-23 18:04     ` Junio C Hamano
2018-07-23 18:38       ` Duy Nguyen
2018-07-23 18:49         ` Duy Nguyen
2018-07-23 21:30           ` Jeff King
2018-07-26  8:12     ` Johannes Sixt

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