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bug#45200: [PATCH] Force Glibc to free the memory freed
From: |
DJ Delorie |
Subject: |
bug#45200: [PATCH] Force Glibc to free the memory freed |
Date: |
Wed, 03 Feb 2021 19:31:56 -0500 |
Stefan Monnier <monnier@iro.umontreal.ca> writes:
>>>> Yet another word of memory used,
>>> Since 200MB is peanuts, I figure that extra 24B should be acceptable ;-)
>> *per chunk*.
>
> No, those counters are meant to be global.
To clarify, that extra word was the "chunk age" information, not the
aggregate metrics.
> One thing that remains a bit unclear for me is in the doc of
> `malloc_trim`; it says:
>
> The pad argument specifies the amount of free space to leave untrimmed
> at the top of the heap. If this argument is 0, only the minimum amount
> of memory is maintained at the top of the heap (i.e., one page or
> less). A nonzero argument can be used to maintain some trailing space
> at the top of the heap in order to allow future allocations to be made
> without having to extend the heap with sbrk(2).
>
> But this only talks about the free space at the "top". Since in our
> case most of the free space is not at the top, I wonder:
> say we have 64KB free at the top and 64MB free elsewhere and we call
> `malloc_trim` with a `pad` of 16MB, will it release ~48MB of the
> non-top free memory or will it free all 64MB of the non-top free memory
> or ... ?
No. Even the tiniest allocation still in use at the top of the heap
locks the entire rest of the heap into memory.
- bug#45200: [PATCH] Force Glibc to free the memory freed, (continued)
- bug#45200: [PATCH] Force Glibc to free the memory freed, Eli Zaretskii, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed, Andreas Schwab, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed, DJ Delorie, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed, Eli Zaretskii, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed, DJ Delorie, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed, Stefan Monnier, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed, DJ Delorie, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed, Stefan Monnier, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed, DJ Delorie, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed, Stefan Monnier, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed,
DJ Delorie <=
- bug#45200: [PATCH] Force Glibc to free the memory freed, Stefan Monnier, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed, DJ Delorie, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed, Stefan Monnier, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed, DJ Delorie, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed, Stefan Monnier, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed, DJ Delorie, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed, DJ Delorie, 2021/02/03
- bug#45200: [PATCH] Force Glibc to free the memory freed, Stefan Monnier, 2021/02/03