On Sun, Mar 24, 2013 at 03:34:33PM +0100, Sebastian Ramacher wrote: > On 2013-03-24 07:28:03, Marwan Tanager wrote: > > This patch tries to solve a serious problem with zathura leaking a > > horrendous > > amount of memory during scrolling through a document. > > > > The problem is that the current way of periodically reclaiming the cairo > > surfaces of the pages widgets is not working at all. The only case in which > > it > > seems to work is the first time (and "only" the first time) the timeout > > function purge_pages is triggered, and even this first time sometimes > > doesn't > > free the memory if it happened while scrolling through the document. > > > > To see it in action, try opening a large document (e.g. 500+ pages), and > > scroll through it by dragging the scrollbar or continuously pressing > > <shift-j>, > > or <shift-k>. Meanwhile, watch the output of 'top $(pidof zathura)' until > > you > > end up with a throttled system riddled with continuous swapping. Zathura > > will > > fiercely eat all the physical system memory while scrolling through a > > relatively big document. > > > > I've spent a while trying to figure out why the memory isn't freed after > > the > > first time the timeout function is triggered, but quite frankly, I couldn't > > manage to get to any reasonable conclusion. Injecting debug messages in > > zathura_page_widget_update_surface shows that all the pages, but the > > current > > visible one, are eventually reclaimed. This means that > > cairo_surface_destroy > > must have been called on every surface of a page that exceeded it's > > end-of-life > > threshold, but without actually doing it's job of freeing the surface > > memory. > > > > So, this patch bypasses this mechanism by freeing a surface as soon as it's > > associated page becomes invisible. Try repeating the same experiment as > > above > > with this patch, and watch the rate of memory consumption drops > > dramatically. I > > scrolled the entire length of a 1300-pages document and the end result was > > 500 > > MB. And I don't think this is leaking memory due to cairo surfaces pixel > > buffers, because it never increases after reaching this limit. Maybe it's > > some > > internal allocations done by GTK or GDK. This doesn't seem very far-fetched > > for > > an application with 1300+ GTK widgets in this case. > > No, please don't. There is reason why we decided to keep the pages in > memory: consider a document with same pages, but one of them takes ages > to render ( has an extreme example of such a file, but any document > with larger images should do). In 0.0.8.x scrolling was a PITA with such > documents: you had to wait until the page was fully rendered to do > anything else.
Personally, I haven't had an encounter with such extreme cases, so I hadn't thought of this, but of course this is something that should be considered. > Keeping the pages in memory for some time is our attempt to improve the > scrolling experience in that case. Scrolling back and forth between two > pages becomes a much better experience since you don't have to wait > until the page is re-rendered to see it. So it's a compromise between > memory usage and time spent to re-render pages. Of course, it's an obvious trade-off, but when it is very unbalanced like in this case (I don't want to sacrifice all of my system memory and crash running applications in order to have a good experience scrolling around a pdf document), that's where we should reconsider doing things. > The code to destroy the cairo surfaces periodically is not optimal, but > if it all, we should fix this portion of the code. Maybe a timing-based > solution is not a good idea and there are better ways to approach this, > but I really don't want to ruin the above use case again. > > Ideas and patches to improve the page reclaiming code are very welcome. That's why I sent the patch in the first place. I didn't actually intend it to be applied, but just to shed some light on the source of the problem. Marwan _______________________________________________ zathura mailing list email@example.com http://lists.pwmt.org/mailman/listinfo/zathura