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From: Konstantin Osipov <kostja@tarantool.org>
To: tarantool-patches@freelists.org
Cc: gorcunov@gmail.com, vdavydov.dev@gmail.com
Subject: Re: [tarantool-patches] [rfc 3/4] core/fiber: Put static watermark into stack to track its usage
Date: Tue, 5 Mar 2019 11:20:29 +0300	[thread overview]
Message-ID: <20190305082029.GL21955@chai> (raw)
In-Reply-To: <20190302130034.050488016@gmail.com>

* Cyrill Gorcunov <gorcunov@gmail.com> [19/03/03 23:25]:
> We want to detect a situation where task in fiber is too eager for
> stack and close to its exhausting. For this sake upon stack creation
> we put 8 marks on last stack page with step of 128 bytes. Such params
> allows us to fill ~1/4 of a page, which does seem reasonable but
> we might change this params with time.
> 
> Since the watermark position is permanent and some task is close
> to stack limit we print about the situation once to not spam
> a user much and stop putting the mark on recycling.
> 
> Closes #3418

As a policy we write meaningful comments for every function, static or not,
obvious or not. The idea of such a comment is to reflect the
author's intent and technical trade-offs considered when designing
a function. The comment should preferably be concise, however.

> +/*
> + * Random values generated with uuid.
> + * Try to fit a cache line.

I don't understand this comment. Since you're putting a poison-gap
between each number, how could you possibly fit a cache line?

> + */
> +static const uint64_t poison_pool[] = {
> +	0x74f31d37285c4c37, 0xb10269a05bf10c29,
> +	0x0994d845bd284e0f, 0x9ffd4f7129c184df,
> +	0x357151e6711c4415, 0x8c5e5f41aafe6f28,
> +	0x6917dd79e78049d5, 0xba61957c65ca2465,
> +};
> +
> +/*
> + * We poison by 8 bytes as it natural for stack
> + * step on x86-64. Also 128 byte gap between
> + * poison values should cover a common cases.

> +	/** Stack watermark addr for overflow detection. */
> +	void *stack_wmark_ofl;

Generally we try to avoid abbreviations unless really necessary.
Why not simply stack_overflow_watermark? 

>  	/** Coro stack size. */
>  	size_t stack_size;
>  	/** Valgrind stack id. */

-- 
Konstantin Osipov, Moscow, Russia, +7 903 626 22 32
http://tarantool.io - www.twitter.com/kostja_osipov

  parent reply	other threads:[~2019-03-05  8:20 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-02 12:55 [rfc 0/4] fiber/stack: Increase stack size and shrink rss usage Cyrill Gorcunov
2019-03-02 12:55 ` [rfc 1/4] core/fiber: Increase default stack size Cyrill Gorcunov
2019-03-02 12:55 ` [rfc 2/4] core/fiber: Mark stack as unneeded on creation Cyrill Gorcunov
2019-03-02 12:55 ` [rfc 3/4] core/fiber: Put static watermark into stack to track its usage Cyrill Gorcunov
2019-03-05  8:08   ` [tarantool-patches] " Konstantin Osipov
2019-03-05  8:17     ` Cyrill Gorcunov
2019-03-05  8:10   ` Konstantin Osipov
2019-03-05  8:14     ` Cyrill Gorcunov
2019-03-05 19:17     ` Cyrill Gorcunov
2019-03-05  8:20   ` Konstantin Osipov [this message]
2019-03-05  8:27     ` Cyrill Gorcunov
2019-03-02 12:55 ` [rfc 4/4] core/fiber: Shrink stack when recycling Cyrill Gorcunov
2019-03-05  8:30   ` [tarantool-patches] " Konstantin Osipov
2019-03-05  8:41     ` Cyrill Gorcunov
2019-03-05  9:32       ` [tarantool-patches] " Konstantin Osipov

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