Reuse the buffer for read/write-through-propolis-heap#1006
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iximeow wants to merge 1 commit intooxidecomputer:masterfrom
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Reuse the buffer for read/write-through-propolis-heap#1006iximeow wants to merge 1 commit intooxidecomputer:masterfrom
iximeow wants to merge 1 commit intooxidecomputer:masterfrom
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iximeow
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Jan 7, 2026
| let iovs = [iovec { | ||
| iov_base: buf.as_mut_ptr() as *mut libc::c_void, | ||
| iov_len: buf.len(), | ||
| iov_len: total_capacity, |
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my first go at this change I'd missed this line in the change, and a small write from the guest went and wrote the whole much larger buffer, garbage and all, into my guest disk. I'd mentioned this morning that I was hesitant about misusing the longer-lifetime scratch buffer and it was really me still processing the shock of having bricked a test image without realizing I'd been playing with fire.
in retrospect, looking at this change, I'm much less anxious about this as a risky change, but I'm still not chomping at the bit to get this in.
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phd failures are not from this change: |
this seems to have some effect, but not a lot; nothing when I/Os are all the same size, on the order of 5% better throughput when I/Os vary between 4 KiB, 32 KiB, 256 KiB, and in-between
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this has some effect, but only in some cases; nothing when I/Os are all the same size, on the order of 5% more IOPS when I/Os vary between 4 KiB, 32 KiB, 256 KiB, and in-between.
since this is here and works I'm.. fine with merging it, but like #985 this builds on, we're just working around an OS bug, so this all gets ripped out when the OS has a real
segvmm_page{un}lock.