From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 27 Mar 2019 13:15:52 +0300 From: Vladimir Davydov Subject: Re: [PATCH 2/2] lib/core/fiber: Allow to extend default stack size Message-ID: <20190327101552.d3b6xvezm3rigszm@esperanza> References: <20190319193845.31221-1-gorcunov@gmail.com> <20190319193845.31221-3-gorcunov@gmail.com> <20190327093506.zsxzchje2un76rcp@esperanza> <20190327094618.GH20626@uranus.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190327094618.GH20626@uranus.lan> To: Cyrill Gorcunov Cc: tml , Konstantin Osipov List-ID: On Wed, Mar 27, 2019 at 12:46:18PM +0300, Cyrill Gorcunov wrote: > On Wed, Mar 27, 2019 at 12:35:06PM +0300, Vladimir Davydov wrote: > > > diff --git a/src/lib/core/fiber.c b/src/lib/core/fiber.c > > > index 922a0bfe8..d3cb18a15 100644 > > > --- a/src/lib/core/fiber.c > > > +++ b/src/lib/core/fiber.c > > > @@ -107,18 +107,25 @@ pthread_t main_thread_id; > > > static size_t page_size; > > > static bool stack_growsdown; > > > > > > +/** Indices in fiber stack sizes (FSS) */ > > > enum { > > > + FSS_IDX_MINIMAL, > > > + FSS_IDX_WATERMARK, > > > + FSS_IDX_DEFAULT, > > > +}; > > > + > > > +/** Fiber stack sizes */ > > > +static size_t fiber_stack_size[] = { > > > /* The minimum allowable fiber stack size in bytes */ > > > - FIBER_STACK_SIZE_MINIMAL = 16384, > > > + [FSS_IDX_MINIMAL] = 16384, > > > + /* Stack size watermark in bytes */ > > > + [FSS_IDX_WATERMARK] = 65536, > > > /* Default fiber stack size in bytes */ > > > - FIBER_STACK_SIZE_DEFAULT = 524288, > > > - /* Stack size watermark in bytes. */ > > > - FIBER_STACK_SIZE_WATERMARK = 65536, > > > + [FSS_IDX_DEFAULT] = 524288, > > > }; > > > > Please avoid unrelated changes. If you want to rename or refactor > > something, do it in a separate patch to ease review. > > > > Anyway, I don't see much point in this change - in Tarantool code it's > > common to use a enum for storing constants. > > These are not constants anymore since we're to ajust the values. Ah, I see. Anyway, I'd leave the constants alone and instead introduce a separate static variable to store the current stack size in, because mixing constants (min_size, watermark) and variables (current_default) in one array doesn't look good to me. > > > > +/** > > > + * Initialize early parameters of the stack > > > + * and setup default variables. > > > + */ > > > +static void > > > +fiber_stack_init(void) > > > +{ > > > + static const char default_size_name[] = "FIBER_STACK_SIZE_DEFAULT"; > > > > There's a risk it may conflict with another environment variable. > > At the very least, we should prefix it with TARANTOOL_. > > > > However, I don't think that using an environmental variable is a proper > > way to go. After all, Tarantool is an application server so we typically > > set system variables right from Lua code. > > > > Can we introduce a function in the fiber module for this? The tricky > > part is that it should change the stack size of the calling fiber, > > I guess. > > Yes, stacks are allocated earlier, and we simply can't adjust already > allocated stack thus we might need to distinguish stack sizes between > cord_main and new fibers. This gonna be hard and I would like to escape > such complexity. Seriously, we should use a hard rule: every stack in > the engine has the same size allocated. > > Lets think -- is there a chance we will have to provide more configurable > settings for early init stage in future? If yes then we should invent > early init stage for lua (or say some json fine in /etc). If no and > there is no chance we might need something else in future, better to > stick with simplier solution as environment variables. Makes sense. But as this is a change in the API, we should consult Kostja (Cc-ed).