On Wed, 20 Jan 2016 08:47:39 +0530 Siddhesh Poyarekar <siddhesh.poyarekar@xxxxxxxxx> wrote: > On 20 January 2016 at 03:44, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > Any thoughts on the obvious back-compatibility concerns? ie, why did > > Siddhesh implement this in the first place? My bad for not ensuring > > that the changelog told us this. > > > > https://lkml.org/lkml/2012/1/14/25 has more info: > > > > : Memory mmaped by glibc for a thread stack currently shows up as a > > : simple anonymous map, which makes it difficult to differentiate between > > : memory usage of the thread on stack and other dynamic allocation. > > : Since glibc already uses MAP_STACK to request this mapping, the > > : attached patch uses this flag to add additional VM_STACK_FLAGS to the > > : resulting vma so that the mapping is treated as a stack and not any > > : regular anonymous mapping. Also, one may use vm_flags to decide if a > > : vma is a stack. > > > > But even that doesn't really tell us what the actual *value* of the > > patch is to end-users. > > The end users needed a way to identify thread stacks programmatically > and there wasn't a way to do that. I'm afraid I no longer remember > (or have access to the resources that would aid my memory since I > changed employers) the details of their requirement. However, I did > do this on my own time because I thought it was an interesting project > for me and nobody really gave any feedback then as to its utility, so > as far as I am concerned you could roll back the main thread maps > information since the information is available in the thread-specific > files. OK, thanks. I was thinking of queueing this for 4.6 to let it bake in -next for a cycle, but quadratic performance is bad and nobody will test such an obscure feature in -next so maybe I'll jam it into 4.5 and we wait and see. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>