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Auto merge of #18412 - bholley:bump_style_stacks, r=bholley

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Increase stack safety margin for stylo

https://bugzilla.mozilla.org/show_bug.cgi?id=1395708

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bors-servo 2017-09-07 13:52:48 -05:00 • committed by GitHub
commit 8868d2223d
1 changed files with 13 additions and 10 deletions
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23
components/style/parallel.rs
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@ -32,23 +32,26 @@ use smallvec::SmallVec;
use traversal::{DomTraversal, PerLevelTraversalData};
/// The minimum stack size for a thread in the styling pool, in kilobytes.
pub const STYLE_THREAD_STACK_SIZE_KB: usize = 128;
pub const STYLE_THREAD_STACK_SIZE_KB: usize = 256;
/// The stack margin. If we get this deep in the stack, we will skip recursive
/// optimizations to ensure that there is sufficient room for non-recursive work.
///
/// We allocate large safety margins because certain OS calls can use very large
/// amounts of stack space [1]. Reserving a larger-than-necessary stack costs us
/// address space, but if we keep our safety margin big, we will generally avoid
/// committing those extra pages, and only use them in edge cases that would
/// otherwise cause crashes.
///
/// When measured with 128KB stacks and 40KB margin, we could support 53
/// levels of recursion before the limiter kicks in, on x86_64-Linux [1].
/// levels of recursion before the limiter kicks in, on x86_64-Linux [2]. When
/// we doubled the stack size, we added it all to the safety margin, so we should
/// be able to get the same amount of recursion.
///
/// We currently use 45KB margins, because that seems to be the minimum amount
/// of head room required by an unoptimized debug build, as measured on [2]. We
/// could probably get away with a smaller margin on optimized release builds,
/// but that would be a pain, and the extra padding reduces stability risk.
/// [1] https://bugzilla.mozilla.org/show_bug.cgi?id=1395708#c15
/// [2] See Gecko bug 1376883 for more discussion on the measurements.
///
/// [1] See Gecko bug 1376883 for more discussion on the measurements.
/// [2] layout/style/crashtests/1383981-3.html
///
pub const STACK_SAFETY_MARGIN_KB: usize = 45;
pub const STACK_SAFETY_MARGIN_KB: usize = 168;
/// The maximum number of child nodes that we will process as a single unit.
///