On Mon, Nov 8, 2021 at 9:59 AM Shivaram Lingamneni <shivaramlingamn...@gmail.com> wrote: > > I'm sending strings delimited by CRLF over a socket. As an exercise, I'm > trying to do it while minimizing the total number of allocations. > > I wrote a demo with two implementations, CopyWithTerminatingNewlines1 and > CopyWithTerminatingNewlines2, both of which copy lines from a `chan []byte` > to an `io.Writer`, inserting delimiting CRLFs. But the results are confusing > to me (Go 1.17.3 on linux/amd64): > > https://gist.github.com/slingamn/e4727ad854bdbe585134af9e55956e12 > > 1. Both implementations are functionally identical, and > `(*net.Buffers)WriteTo` gets specialized to writev(2) at runtime > 2. If I'm interpreting the disassembly correctly, > CopyWithTerminatingNewlines1 allocates a new net.Buffers on every iteration > of the loop, while CopyWithTerminatingNewlines2 does not > 3. This is because (*net.Buffers).WriteTo causes the net.Buffers to escape to > the heap > > But I'm not sure why this is the case --- am I doing something wrong, or is > this a limitation of the escape analyzer that could in principle be improved, > or is there some essential reason for this?
It's because the (*Buffers).WriteTo method makes a method call on an interface type, and the compiler doesn't know whether the method causes the Buffers argument to escape or not. This could be improved in principle but I think it would be hard. Ian -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CAOyqgcWCBidgo6kii_4LFCtWvdrapOXJ-nRQx3CL%3DvpPg%2BOPoQ%40mail.gmail.com.
