https://share.firefox.dev/3PPYuRI This shows up a lot in a speedometer (around 4%), and skews comparisons with Chrome as both browsers take timestamps in different places, though appear to be similarly affected overall. This occurs on several devices I have tested including the Samsung A51, Samsung S9, Pixel 5, OnePlus 8 Pro. On other devices this barely shows up in profiles if at all. It appears that the VDSO fast path is failing for some reason and we end up doing a syscall. I'm trying to get kernel symbols included in the profile to see if that sheds any light on why. We may need to audit our usage of timestamps on the critical path.
Bug 1843534 Comment 0 Edit History
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https://share.firefox.dev/3PPYuRI This shows up a lot in a speedometer (around 4%), and skews comparisons with Chrome as both browsers take timestamps in different places, though appear to be similarly affected overall. This occurs on several devices I have tested including the Samsung A51, Samsung S9, Pixel 5, OnePlus 8 Pro. On other devices (including Pixel 4, PIxel 6, Samsung S10) this barely shows up in profiles if at all. This isn't a exynos vs snapdragon type thing. Additionally, naively checking the kernel version doesn't show a pattern: if this was broken then fixed in specific versions then perhaps vendor specific backports muddy the water. It appears that the VDSO fast path is failing for some reason and we end up doing a syscall. I'm trying to get kernel symbols included in the profile to see if that sheds any light on why. We may need to audit our usage of timestamps on the critical path.