-*- text -*-
-From: Godmar Back <godmar@gmail.com>
-Subject: project 4 question/comment regarding caching inode data
-To: Ben Pfaff <blp@cs.stanford.edu>
-Date: Sat, 14 Jan 2006 15:59:33 -0500
-
-Ben,
-
-in section 6.3.3 in the P4 FAQ, you write:
-
-"You can store a pointer to inode data in struct inode, if you want,"
-
-Should you point out that if they indeed do that, they likely wouldn't
-be able to support more than 64 open inodes systemwide at any given
-point in time.
-
-(This seems like a rather strong limitation; do your current tests
-open more than 64 files?
-It would also point to an obvious way to make the projects harder by
-specifically disallowing that inode data be locked in memory during
-the entire time an inode is kept open.)
-
- - Godmar
+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.
+
+- 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 <godmar@gmail.com>
Subject: on caching in project 4
workload might not force any cache replacement, so the eviction
strategy doesn't matter.)
-Godmar Back <godmar@gmail.com> 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.
* Finish writing tour.
-* Introduce a "yield" system call to speed up the syn-* tests.
-
via Godmar Back:
-* Project 3 solution needs FS lock.
-
* Get rid of mmap syscall, add sbrk.
-* Make backtrace program accept multiple object file arguments,
- e.g. add -u option to allow backtracing user program also.
-
* 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
* Internal tests.
-* Improve automatic interpretation of exception messages.
-
-* Userprog project:
-
- - Mark read-only pages as actually read-only in the page table. Or,
- since this was consistently rated as the easiest project by the
- students, require them to do it.
-
- - Don't provide per-process pagedir implementation but only
- single-process implementation and require students to implement
- the separation? This project was rated as the easiest after all.
- Alternately we could just remove the synchronization on pid
- selection and check that students fix it.
-
* Filesys project:
- Need a better way to measure performance improvement of buffer
- Add extra credit:
- . Low-level x86 stuff, like paged page tables.
-
. Specifics on how to implement sbrk, malloc.
. Other good ideas.
- . 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.
projects / pintos-anon / blobdiff