Hi,
> This wouldn't really work because FPM does not control the script during >> execution and would have to check it out after each allocation which is not >> really viable. >> > > Thanks for the feedback! I agree that monitoring memory usage after each > allocation would be infeasible. However, my suggestion was actually to > check memory usage *only once per request*, specifically at request > shutdown, when FPM regains control and before assigning another request to > that worker. > > I think that would require a different name because it would not reflect max memory usage in any way - it would be measured at the time when the memory usage is lowest. We could maybe set some options that would measure the maximum of increase of memory between requests - I mean difference between lowest memory usage (most likely after the first request) and then compare against current usage after the latest request and set limit on this difference. Not sure about the name for that. Maybe something like pm.max_memory_increase or something like that. > We already have hooks for request startup and request shutdown in FPM. > Could we simply insert a memory check at the request shutdown stage—where > the worker is returning control to the FPM master process—before picking up > a new request? > > Yeah that would be possible. > Just to be clear, "memory_limit" helps kill runaway scripts mid-request. > By contrast, the newly proposed pm.max_memory is meant to catch processes > with a slow leak across multiple requests. We only need to check at the end > of each request, which is presumably when the worker returns control to FPM. > There is one thing to note that memory_limit actually measure only memory allocated through the per request php memory allocator so it's not actually limit on total usage including the standard allocator memory usage. So there would be still a use case for total limit using cgroups but I agree that the more important use is to catch slow leaks which the above should help with in a better way than pm.max_requests. Regards, Jakub
