X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=TODO;h=a4e3e31c080d3a2d5f0a004ec08f10e1d05bc540;hb=4b9c6406e80d1fe9e5aa236e0d34dadbc4703307;hp=7d6ba406ed2365122dc213cb8b30da257f582db2;hpb=31711e65718e8334dbb672eca64b6b4b906d1a03;p=pintos-anon diff --git a/TODO b/TODO index 7d6ba40..a4e3e31 100644 --- a/TODO +++ b/TODO @@ -1,30 +1,102 @@ -*- text -*- +Godmar says: + +- In Project 2, we're missing tests that pass arguments to system calls +that span multiple pages, where some are mapped and some are not. +An implementation that only checks the first page, rather than all pages +that can be touched during a call to read()/write() passes all tests. + +- In Project 2, we're missing a test that would fail if they assumed +that contiguous user-virtual addresses are laid out contiguously +in memory. The loading code should ensure that non-contiguous +physical pages are allocated for the data segment (at least.) + +- Need some tests that test that illegal accesses lead to process +termination. I have written some, will add them. In P2, obviously, +this would require that the students break this functionality since +the page directory is initialized for them, still it would be good +to have. + +- There does not appear to be a test that checks that they close all +fd's on exit. Idea: add statistics & self-diagnostics code to palloc.c +and malloc.c. Self-diagnostics code could be used for debugging. +The statistics code would report how much kernel memory is free. +Add a system call "get_kernel_memory_information". User programs +could engage in a variety of activities and notice leaks by checking +the kernel memory statistics. + +From: "Godmar Back" +Subject: set_priority & donation - a TODO item +To: "Ben Pfaff" +Date: Mon, 20 Feb 2006 22:20:26 -0500 + +Ben, + +it seems that there are currently no tests that check the proper +behavior of thread_set_priority() when called by a thread that is +running under priority donation. The proper behavior, I assume, is to +temporarily drop the donation if the set priority is higher, and to +reassume the donation should the thread subsequently set its own +priority again to a level that's lower than a still active donation. + + - Godmar + +From: Godmar Back +Subject: on caching in project 4 +To: Ben Pfaff +Date: Mon, 9 Jan 2006 20:58:01 -0500 + +here's an idea for future semesters. + +I'm in the middle of project 4, I've started by implementing a buffer +cache and plugging it into the existing filesystem. Along the way I +was wondering how we could test the cache. + +Maybe one could adopt a similar testing strategy as in project 1 for +the MLQFS scheduler: add a function that reads "get_cache_accesses()" +and a function "get_cache_hits()". Then create a version of pintos +that creates access traces for a to-be-determined workload. Run an +off-line analysis that would determine how many hits a perfect cache +would have (MAX), and how much say an LRU strategy would give (MIN). +Then add a fudge factor to account for different index strategies and +test that the reported number of cache hits/accesses is within (MIN, +MAX) +/- fudge factor. + +(As an aside - I am curious why you chose to use a clock-style +algorithm rather than the more straightforward LRU for your buffer +cache implementation in your sample solution. Is there a reason for +that? I was curious to see if it made a difference, so I implemented +LRU for your cache implementation and ran the test workload of project +4 and printed cache hits/accesses. +I found that for that workload, the clock-based algorithm performs +almost identical to LRU (within about 1%, but I ran nondeterministally +with QEMU). I then reduced the cache size to 32 blocks and found again +the same performance, which raises the suspicion that the test +workload might not force any cache replacement, so the eviction +strategy doesn't matter.) + +Godmar Back writes: + +> in your sample solution to P4, dir_reopen does not take any locks when +> changing a directory's open_cnt. This looks like a race condition to +> me, considering that dir_reopen is called from execute_process without +> any filesystem locks held. + * Get rid of rox--causes more trouble than it's worth * Reconsider command line arg style--confuses everyone. -* pintos script doesn't (always?) delete temp disks - * Finish writing tour. via Godmar Back: -* Project 3 solution needs FS lock. - * Get rid of mmap syscall, add sbrk. -* hash_destroy() should take function arg. - -* Make backtrace program accept multiple object file arguments, - e.g. add -u option to allow backtracing user program also. - -* VM projects do not use enough memory to force eviction. - Should reduce user limit or increase memory consumption. - - - +* page-linear, page-shuffle VM tests do not use enough memory to force + eviction. Should increase memory consumption. +* Add FS persistence test(s). * process_death test needs improvement @@ -72,3 +144,66 @@ via Godmar Back: . opendir/readdir/closedir . everything needed for getcwd() + +To add partition support: + +- Find four partition types that are more or less unused and choose to + use them for Pintos. (This is implemented.) + +- Bootloader reads partition tables of all BIOS devices to find the + first that has the "Pintos kernel" partition type. (This is + implemented.) Ideally the bootloader would make sure there is + exactly one such partition, but I didn't implement that yet. + +- Bootloader reads kernel into memory at 1 MB using BIOS calls. (This + is implemented.) + +- Kernel arguments have to go into a separate sector because the + bootloader is otherwise too big to fit now? (I don't recall if I + did anything about this.) + +- Kernel at boot also scans partition tables of all the disks it can + find to find the ones with the four Pintos partition types (perhaps + not all exist). After that, it makes them available to the rest of + the kernel (and doesn't allow access to other devices, for safety). + +- "pintos" and "pintos-mkdisk" need to write a partition table to the + disks that they create. "pintos-mkdisk" will need to take a new + parameter specifying the type. (I might have partially implemented + this, don't remember.) + +- "pintos" should insist on finding a partition header on disks handed + to it, for safety. + +- Need some way for "pintos" to assemble multiple disks or partitions + into a single image that can be copied directly to a USB block + device. (I don't know whether I came up with a good solution yet or + not, or whether I implemented any of it.) + +To add USB support: + +- Needs to be able to scan PCI bus for UHCI controller. (I + implemented this partially.) + +- May want to be able to initialize USB controllers over CardBus + bridges. I don't know whether this requires additional work or if + it's useful enough to warrant extra work. (It's of special interest + for me because I have a laptop that only has USB via CardBus.) + +- There are many protocol layers involved: SCSI over USB-Mass Storage + over USB over UHCI over PCI. (I may be forgetting one.) I don't + know yet whether it's best to separate the layers or to merge (some + of) them. I think that a simple and clean organization should be a + priority. + +- VMware can likely be used for testing because it can expose host USB + devices as guest USB devices. This is safer and more convenient + than using real hardware for testing. + +- Should test with a variety of USB keychain devices because there + seems to be wide variation among them, especially in the SCSI + protocols they support. Should try to use a "lowest-common + denominator" SCSI protocol if any such thing really exists. + +- Might want to add a feature whereby kernel arguments can be given + interactively, rather than passed on-disk. Needs some though.